It happens sometimes that a user removes his comment(s). I think it is okay when nobody replied to them. However, when other people already replied to them, their time writing the replies was spent for nothing. To avoid this, I would like to suggest a feature request that blocks the removal of a comment by the author which was already quoted.
- Difficult to decide when a comment should be considered as quoting another comment.
- Not an expected behavior - we'd get endless meta threads "Why can't I delete my comment?"
- Too easy to abuse (one could maliciously prevent someone else from deleting comments).
- Not worth the SE team's time and effort to implement this just to save you the inconvenience of writing a new comment.
If one of the users in a comment conversation decides that his part should be removed, it is usually a sign that the comments have become either obsolete or non-constructive. Removal of the whole comment thread is a good thing in those cases.
Prohibiting the removal of quoted commments would make it impossible to ever remove any conversations except for laboriously removing the comments backwards, one at a time (which would have to be coordinated between the participating users).
Your proposal would make it effectively impossible for the community to remove any longer comment threads, which is rather harmful in my opinion.
Sometimes this feature would be fine - particularly here in the discussion threads. However, on the main site this would have a negative net effect.
I have been a party to many an exchange of the following kind (at both the giving and the receiving end): 1) somebody posts an answer that is of a high quality, but has a minor mistake, 2) somebody else points it out in a comment, 3) the original author fixes the error and leaves a thank you note. Often enough at this point the sequence of comments no longer serves a point, and is deleted in its entirety.
There are longer versions and variations to this basic exchange.
I view the removal of such exchanges as a form of professional courtesy. I feel that leaving those comments would distract future readers. The comment served its purpose, the help was acknowledged, pleasantries were exchanged - time to move on.
I'm sad to say I may not have remembered to remove all my comments that would fit this description. May be one party or the other had to do something else, and the matter was forgotten?
If this (math.SE that is, not meta) was a discussion forum, I would agree with you. I'm a new user to stackexchange, but have some experience from various forums. In the beginning I found it confusing when comments had been removed and answers to non-existing questions popped up out of the blue.
I was also confused by the selection process for comment previewing when there are a lot of comments to a post. I still don't really get it, but it definitely have something to do with the number of upvotes. Nevertheless, it chops up the discussion thread and it's hard to follow what's being debated unless you view all the comments.
I think the important issue here is that this is not primarily a discussion forum, it's a Q+A site. I guess one important goal is that a future visitor should quickly be able to find the answer to his/her question without needing to go through several pages of discussion.
With this in mind, I think the way it works today is fine, primarily because it kind of discourages (or at least does not encourage) the use of the comment field for permanent discussion.