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.
- Obvious SPAM --> should be deleted
- Comments with obviously no useful content like "+1 you ROCK" (for those there are upvotes) --> should be deleted
- 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.
- "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.
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.