It has been suggested in this question that comments should be for the purpose of clarification of a question or answer, and that eventually the clarifications should be editted into the question/answer so that people don't have to look down the comment change to see what was "really" meant.

We took up a policy of removing irrelevant comments, but it seems that the issue is larger now than just dealing with noise in comments.

When, if at all, should we delete comments? For that matter, is there any reason that comments should not just be deleted after a certain period of time? They can be fun to read, but do comments truly serve any purpose 6 months after they were posted if questions are being properly edited?

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if questions are being properly edited - That's a big "if". –  Anna Lear Sep 7 '11 at 19:56
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Since answers took off in a more general direction of discussing comment deletions, I edited the question to be more general as well. Hope you don't mind. –  Anna Lear Sep 9 '11 at 5:13
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6 Answers 6

I say comments should stay around forever. In fact, I think that fewer comments need to be deleted overall. Comments serve as kind of a record of how the answer developed. Sure, some of the comments might not be relevant, but the dialog that they capture shows how an answer is understood and (if it's edited) evolves over time. It tells a story that the edit history really doesn't, and that's collaboration between multiple people to build "the perfect answer".

And before someone mentions the chat, right now, I don't feel it's suitable for this purpose. To the best of my knowledge, there's no way to tie chats into questions. The chat also seems so wrong for this purpose. As nice as having chat functionality is, a lot of what happens on a Stack Exchange is asynchronous - questions, answers, and comments are asynchronous while chat just means you have to go to another page/part of the site and it introduces a more synchronous feel to it.

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Posts have a revision history for the specific purpose of being able to see how they evolved. Comments don't reflect this, and in nearly every case of comment cleanup, the comments have precious little to do with the final state of the post to which they're attached. –  user8 Sep 8 '11 at 3:06
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@Mark However, they don't capture the discussions and exchanges between people to lead them there. Perhaps that's a flaw with revision history and comments on the post should also be versioned. Also, very few people add meaningful revision comments explaining why they changed a post, so I can see what changed, but I also like to know what lead to drive those changes. –  Thomas Owens Sep 8 '11 at 12:17
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Disclaimer: in this answer, I'm assuming comments' content is not offensive, insulting, or otherwise not in keeping with the spirit of the "Be nice" guideline.


I think there are two things to tackle here:

  1. automatic deletion of comments;
  2. manual deletion of comments and removal of some discussions.

Should we automatically delete comments after some time? Absolutely not. While it is true that extended discussion in comments is discouraged universally across the Stack Exchange network, there is still value in comments that add supporting information. Ideally that information should be edited into the answer, but that doesn't always happen.

Comments on questions serve the purpose of someone being able to add a helpful hint that might just be a guess or otherwise not fit to stand on its own as an answer.

There is absolutely no way to automatically or manually ensure that all information given in a comment is preserved in a question or an answer. This leaves us with some comments that are more noise than signal. Those we have to remove as we find them. When I say "we" here I mean both the community and the moderators. As moderators, we typically react to flags on comments, but given enough flags on a comment, it will be removed automatically without our intervention.

Comments have always been and probably will continue to be second-class citizens on the network. That is entirely by design and that's shown in the limitations that comments have:

  • comments have a length limit;
  • there is no downvoting on comments, so they are not subject to the usual community vetting of their quality;
  • comments do not affect reputation;
  • comments are collapsed when their number exceeds 5;
  • moderators see an automated "more than 20 comments posted" flag on posts that generate a lot of comments in a short amount of time.

The design of each site places primary focus on questions and answers. We want all useful information required to answer a question to ideally be in an answer. How that answer was developed is largely unimportant so long as the final product of that development is valuable. How valuable it is can be determined through up and down votes on the answer.

Stack Exchange set out to "make the internet better" by creating an environment where the best information rises to the top. Asking the user to dig through a lengthy comment thread on the off chance that the information they're looking for is there goes completely counter to that mission. If we're going to allow that, we might as well just abandon this whole Q&A idea and go back to forums where readers can already sift through pages of unrelated or possibly contradictory information.

For an example, compare the comments between Rook and me on his answer. Is it really beneficial to have our discussion there or is it better for him to express his point in his answer and for me to express mine here? In my opinion, reading one coherent answer is infinitely better than reading a string of broken up comments. Granted, meta posts are a bit of a special case since here we encourage discussion, but I think this still illustrates my point.

I do think we can be better about defining extended discussions and clearing up comment threads. We can discuss that here.

I know it can be difficult to watch your comments be removed and I apologize for that. I know the chat isn't perfect in many ways, and I apologize for that too. But at the end of the day, comments are designed to be transient.

For what it's worth, as moderators we typically only respond to comment flags from community members and to the automatic "more than 20 comments posted" flag as those are usually a good indication that something might be going off-track. It's not typical for posts to generate large amounts of comments in a short amount of time. We do not (far as I know) go out looking for comments to delete.

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I agree with most of what you said, so I won't go to dispute the parts that I don't agree with, but I still think you put it rather vaguely. There should be stronger guidelines in place for what should and what shouldn't be deleted; otherwise we're back to square one - the whim of the moderator of the day ... which is pretty much where we started, only with a "Sorry about that ol'chap. Better luck next time." inserted. –  Rook Sep 11 '11 at 16:51
    
@Rook I welcome any and all suggestions for what the stronger guidelines could look like. :) In my experience, it's difficult to nail down a precise guidelines on something that's inherently subjective, but I may be looking at it differently than you are. –  Anna Lear Sep 11 '11 at 19:36
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I agree with Thomas. Comments often contain good supporting (or refuting) points related to the answer, or contain other valuable nuggets of information who's worth may not be immediately evident. I've spent many years on the net digging up hints to solving obscure programming problems - and I cant tell you how many times an 'answer' or an important 'clue' was found in some post made in a forum or blog that was only tangental to their topic, but critically important to me. So you never really know what information will be valuable in the future. I see no reason to ever delete them. Maybe stack can just allow users to ignore comments if they dont see the value in them.

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My viewpoint which coincides greatly with the ones already made by Thomas, GrandmasterB and maple, is that we should not embrace a policy by which comments serve only for the purposes of clarification an answer. Since rules on this site are alredy applied retroactively (something else which I am also opposed to, since that puts us in the ex post facto situation, which is not, let's say expected, but let's leave that aside for now) that would put the majority of all comments in line for deletion.

It is my view that yes, although comments don't always serve the purpose of clarification; sometimes they only tangentially touch the answer's topic, they are in many cases a source of valuable information! Or funny (yes, I cherish those as well).

In the ideal world, an answer would be posted by the author, after which an "extended" comments discussion of no more than 3 comments per person(!) would be led in hope of clarifying the finer points of the answer. If it took longer than that, it would be moved to chat, after which an author would come back and amend the answer.

However, this is real world. I don't know them or can't speak about the habits of others, but I'm a fella who has a life. Meaning, first, I don't stare at these forums all day waiting for someone to post a comment so that I could think about it and immediately change my answer. Sometimes I don't change it at all (just don't feel editorial at the moment). Sometimes somebody posts a comment, to which I don't reply at all but come back to after two weeks after thinking about it, or after something else reminds me of something I saw in that comment. Sometimes somebody posts a link or a Did you know tip which I would never include in my answer, but which adds to the topic at hand very nicely.

Chat is not an adequate comments replacement. Not only it (not sure about this, but someone will set me right if I'm wrong) disables those who have not commented first to see the current discussion, but it forces them to comment something (which has possibly already been said) to even "join the discussion". Also, if the chat room holds several comments (which are not necessarily clarifying the answer) but less than 15 (so I've heard) it is not kept, therefore effectively losing its contents.

To put it short, the system of answers and comments as it was put in the beginning and up until relatively recently worked very well. Comments were not deleted (Why should they, after all? Are they taking that much space on the server's hard drives that they cannot be kept?) and the interface and joining in to see what is currently discussed was easy and intuitive. Also, history was kept.

The only comments which I exclude from that rule, are the ones containing obvious SPAM which was easily delt with with the 5 second (or something like that) delay in posting and through the flagging system. In any case, those were easily recognized. Those containing obviously useless bits like "+1 you rock" would also fall into this category.

They can be fun to read, but do comments truly serve any purpose 6 months after they were posted if questions are being properly editted?

Why 6 months? Why not two? Or twelve?

And what after that? Will we start deleting answers as well? Questions also, while we're at it? After all, after a certain time, most things lose their purpose. That doesn't mean we should suddenly kill and get rid of it.

And who is to say whether something is for deletion? Moderators? (It's a nice model. On a community shaped site, two or three persons having the power to decide to single handedly delete and shape content to their liking, without any discussion or warning, possibly even to the level of completely changing the original author's meaning. ... No, sorry, I don't buy it.

History should be kept intact, wherever we like it and agree with it or not.


Update: My modest opinion on what should and when it should get deleted.

  1. Obvious SPAM --> should be deleted
  2. Comments with obviously no useful content like "+1 you ROCK" (for those there are upvotes) --> should be deleted
  3. Comment which clarifies a question or an answer, or which inquires about a point mentioned in the question or an answer.
    a) After a finished discussion with the author, the author decides whether to delete his own comments after implementing them in an answer. The other side is strongly suggested to do so too. If the contents of the comments have already been included in the answer the moderator will first warn the author that they will be deleted, after which he will do so (within approximately 12-24 hours). That way the author can check whether there is any remaining valuable information in the comments which he considers worth keeping. He can object to the deletion, after which that discussion must be settled before the moderator deletes the aforementioned comments. The moderator will not by his own hand delete comments at the refusal of the author, unless they're SPAM, hate speech or those falling into one of the similar categories.
    b) An unfinished discussion with the author is in progress - comments stay.
    c) A tip which tangentially adds to the answer topic but will not be included in the answer by the author - comments stay.
  4. "Insult matches" as Anna nicely puts it - will be deleted by the moderator after a previous warning some time before to the participants to stop with that kind of talk. Hate speech, political talk and alike included.

To put it short, I am against most deletions of comments (except the obvious SPAM, hate speech et cetera) by the moderators without any consultations with the authors of the mentioned comments.

Why?

Because we already have several categories of users with the capability to change content at will(!) - and if we accept the policy that they can delete content as well, then it is just a step away from having complete and utter control over content still signed by you. In analogy it is like you gave away a bianco check to someone who you do not know, lest alone agree with.


2nd update :: @Anna - reply to your last comment - I couldn't put this in a box down below, therefore ...

"discussions that veer off-topic and no longer clarify the answer"; well, first, who's to say what's offtopic? I have serious doubts that moderators who review hundrers of questions every day can just jump in and, in a few seconds, see all the intricate details of the discussion at hand. Something which may seem at first hand "obviously" offtopic can lead to a very ontopic conclusion two comments later which the author will append to his answer and which will indeed augment its value. Can the moderators know what either the comenteer or the author are thinking, or where are they getting in their discussion (expecially in the area they are less familiar with)? - I doubt it.

Therefore, I say let them talk. Do not just jump in! BUT, as already hinted in my answer, they can't talk forever (so to say). The discussion in the comments has to finish eventually and its conclusions should be implemented in the answer. So - leave them to it; if neither has posted a comment for, let's say, 2-3 days (to account for the weekends) means they have come to some sort of conclusion, whatever it may be, and the moderator can ask (and I can't emphasize the "ask" part enough) the author of the question to "close it up" (if he/she has not already done so), implement its results in the answer and "clear up the space below". The author gives his opinion and does accordingly or argues that the discussion is still going on, only the other side has been detained at the moment (the maximum time the other side can be detained <- decide on something reasonable - a week?).

I think by now you see where this is going. I'm advertising the principle in which people can talk about whatever, only the talk has got to finish at one point and the authors have got to "clean up afterwards", with the emphasis on the authors cleaning it up. That way the "ones whos name we do not mention" still keep their principle - that the first class citizens are answers - working, and the users do not get the feeling of oppresive "big brother" moderators hanging about their heads (the movie "Brazil" comes to mind here).

Whose side are you really on Jack?

As to your other example, I'll skip it for now, to instead explain my views on why I so persist on this approach. I don't doubt that you realize there are many (infinite?) number of cases not covered here; it would be unwise to even expect that indeed all cases can be covered. So I'm not concerned about that at all.

What I am concerned about is the change of original meaning. I'll elucidate in a bit. Just like usenet and some "forums" (in wide sense of the word) this site's content is also "mirrored" in a few places ("mirrored" may not be the exact term, but its contents are transferred. I've seen my questions posted on this site along with all the answers, on a few others by several occations by now - usually packed in some inferior interface). Meaning that at some point some "thing" comes and picks up the content of some question. It does not update them, nor does it modify them afterwards. The mirror site is not "dynamic" like this one. It just takes a "snapshot" of this one at a certain time.

Now the problem with deletions of comments, expecially if they're done in a middle of a discussion is that it can result in a change of meaning. What the author originally was saying, 2 deleted comments later is not that anymore. I strongly, as I'm sure many others do, object to being signed below something I had no intention of saying. To which that situation can easily lead to. That's why I insist on keeping history, and that's why I object to changing someone's words without their consent and without leaving any traces behind (as moderators do).

The content on the internet nowadays is easily searchable, and also very hard-to-remove once it's "in there". I don't mind that my "content" already "belongs" to the owners of this site, but I'd like to have it retain my meaning. I don't want to one day find my name below something I may or may have not said (I won't be able to remember, naturally), just because there were intermittent sudden changes by a third party. Do you?

*This is not by far the only reason / the only loophole, but it's the most simple one to explain in a few words.

This is a sort of a moderate policy, since IMO, you will still be losing valuable content from the comments that the author didn't implement in his own question, while the commenteer didn't think them being enough to form an independent answer. You will also be losing a humane side to this site, which it had in the beginning. If it is not lost already.

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Nobody is required to comment before being able to see the chat discussion. As I mentioned earlier in another thread, rooms are fully public and anyone can read. (Although there is a 20-reputation minimum required for posting, but that's actually better than the 50-rep minimum required to post comments on the site.) –  Anna Lear Sep 8 '11 at 20:01
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@Anna - I provided I could be wrong in that segment. But one thing interests me still. I just went over a few top viewed questions on SO, and I can't find one instance of that welcome to chat thing. stackoverflow.com/questions/7073484/… doesn't have it. stackoverflow.com/questions/7153659/… doesn't have it. ... Do you know of one question, off hand, where I could "try" that interface? Where is the button that connects the question/answer with its chat room? –  Rook Sep 8 '11 at 20:13
    
There is no button. It is something that's triggered when a certain comment threshold is reached. You can see an example here: meta.programmers.stackexchange.com/questions/1764/… –  Anna Lear Sep 8 '11 at 20:19
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@Anna - I still don't see anything in there except the screenshot. So let me just try to picture it. Say Anna and balpha (from the screenshot) were discussing something, and after a certain threshold "move this to chat" option appeared. You clicked on it, and moved the contents of the so far talk to chat. Now I come along, a passing visitor. What do I have to do to see the so far talk between you and balpha? –  Rook Sep 8 '11 at 20:50
    
The second thing I have with this system is that it is, well impractical. The comments had a simple interface - I could view the question, and without leaving the page leave 10 comments on 10 different answers below. Does introducing chat means I will have to open 10 more(!!) pages in the browser? –  Rook Sep 8 '11 at 20:53
    
Here's an example: programmers.stackexchange.com/questions/102649/…. There's a comment auto-inserted into the thread that points to the chat room. –  Anna Lear Sep 8 '11 at 20:53
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For your second thing, that's a bit of a strawman argument. Not every comment needs to go to chat nor does every discussion get moved either. Seriously, we only come in to clean up comments when they start derailing (turning into insult matches or going off on tangents unrelated to the question) and someone flags the post or when we see a "20 comments posted" auto-flag. We don't go out comment-hunting just for the sake of something to do and we are careful to not remove comments that add valuable information as much as possible. –  Anna Lear Sep 8 '11 at 20:55
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With all that said, I do oppose automatic deletion of comments that's proposed in this meta question. Comments can only be judged on a case-by-case basis with the possible exception of comments like "+1 you rock", which only add noise. –  Anna Lear Sep 8 '11 at 20:55
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I'm not a web designer (or anything remotely similar) so I have no idea to the feasibility of this, but wouldn't it be better (this is an idea that always seemed natural to me for the comments) to try to implement some sort of system similar as it is now, but where comments which are replies to other comments show as subcomments to the first one (think Windows explorer; folders and subfolders system and those [+] thingies that open/close'em up). Closing the top one closes all branches "below". That way let's say two individuals can discuss some feature without bothering everyone else. –  Rook Sep 8 '11 at 20:58
    
Comment threading has been brought up on Meta Stack Overflow a few times and denied every time. I believe that the Powers That Be consider comments second-class citizens and aren't inclined to implement features that encourage comments. They want to focus on questions and answers instead. I gotta head AFK for a while now, but I'll try to dig up a couple links on this later. –  Anna Lear Sep 8 '11 at 21:02
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@Anna (removing comments) Agree; insult matches should be removed (for that purpose, now that I think of it, chat is more than suitable :-) with a previous warning that such language will not be tolerated (for it should not be). But, "going off on tangents" and removing "valuable" information is a gray area. Who is to say what has (except in the obvious black on white cases) "gone off on tangent" and what is "valuable"? I'm opposed to such actions done by a subjective whim of an individual, because when that individual wakes up on a wrong foot, half a –  Rook Sep 8 '11 at 21:30
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day of my commenting goes to trash in 10 seconds or less. And since he gives no warning, I've no chance to explain why that particular bit was valuable. Deleted content in any case cannot be brought back. Reminds me of that crazy law proposal that was brought somewhere, which states that one can shoot another if one "feels" that the other will do him harm. –  Rook Sep 8 '11 at 21:30
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@Anna - No, I'm not against the idea that other people can edit my content. I'm against the idea that they can do so without leaving a trace! Editing the answers is "recorded"; what has been changed, when and by who. As when the comments are in question, they just poof ... dissapear. –  Rook Sep 12 '11 at 14:57
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@Anna - Yes, I've noticed. Only it is volontary and not always done (Very courteous of Mark Trapp to provide an example just a moment ago at programmers.stackexchange.com/questions/108035/… :) And besides, who's to tell they were there in the first place? Why not implement some sort of "Comment deleted by ___" which is shown automatically? (Now will come the part about the dev. costs and how that is not planned. But if community's wishes do not mean anything, then why pretend at all you (well, not you personally) –  Rook Sep 13 '11 at 22:34
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listen to them? I believe, I'm not being the only one who is currently unsatisfied[*] with how comments and moderation in that area is handled. programmers.stackexchange.com/questions/89266/… as just one example - notice the interesting ratio of votes on the deletion message and those on the comment opposed to deletion.) In any case, I'm gonna slowly start ending this discussion on my side for now - I believe we've understood each other on how we stand ... my stand is either not deleting any (and I do mean any!) or in great –  Rook Sep 13 '11 at 22:34
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The dialog to flag a comment reports the reasons for which a comment should be deleted:

  • rude or offensive
  • not constructive/off-topic
  • obsolete
  • too chatty

For example, if I add a comment to make clearer what said in an answer, or I report under which conditions the answer is correct, and the answer is corrected basing on my comment, then my comment is obsolete; if the answer is not changed, then my comment should be left. That is true also when I warn the future users about the risks connected with the solution reported in the answer, or when I report exactly in which cases the solution should be adopted.
I don't think that comments should be automatically removed; they should be removed if they are not useful to the future readers of the answer.

The same is true for questions, and for comments that, for example, ask to the OP what exactly he meant with a specific sentence used in the question.

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Comments add a lot of pertinent information, and history as to how certain information was determined. I think searching previous question on SE sites for related queries would be useless without them.

With that being said there are a lot of extended "chat sessions" that spring up and the only thing preventing them are a moderator scolding.

Perhaps we can have a vote system for comment deletion much like for question closing?

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Comments can be flagged and 3 + Score / 3 flags will delete them unless a moderator steps in to either dismiss the flags or delete the comment earlier. Comment flags age away after 4 days if no action is taken on them and they fail to achieve the flag threshold. –  Anna Lear Sep 8 '11 at 18:17
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