There is an article. It contains a typo. Someone mentions it in a comment. The comment is upvoted as helpful. Author fixes the typo. Now there is a no-longer-useful comment in the discussion, sometimes with replies (the author saying "thanks, fixed", etc.). Sometimes it sits at the top of the discussion, if it was sufficiently upvoted.
If I try to avoid this, I send the author a private message. This does not clutter the discussion, but the disadvantage is that other people don't see me doing this -- so they are likely to also send private messages to the author, and maybe someone will make a comment anyway.
Downvoting the comment gets it out of the way, but it's not fair to the person who made it. We should encourage reporting typos, definitely not punish it.
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My proposal is to make a new functionality that approximately means "this comment was useful at the moment it was made, but it has outlived is usefulness". Available in the three-dots menu in the upper-right corner of the comment.
A comment can be marked like this by the person who made it, or by the author of the article. (Or by the moderators, of course.) A comment marked like this will be moved to the bottom, regardless of the sorting mode, and will by default appear collapsed. (Maybe also displayed using a different color.)
Unlike retraction, this has no impact on voting, etc. (I am not 100% sure how retraction works.) You can still read the comment, even upvote it if you wish. It just doesn't get in the way. Also, semantically, there is a difference between "I no longer support this" and "this is no longer relevant, but it was when I wrote it".
Both, although collapsing more than sorting. A few things -
I would be fine if this was combined.
The post starts off by talking about typos, but then says "this comment was useful at the moment it was made, but it has outlived is usefulness" - which covers far more than just typos.
The current moderation is bad enough for this; it's a whole lot easier to detect bad-faith 'removing comment entirely' than it is to detect bad-faith 'I did an edit that (didn't actually) address(ed) this point, so this comment no longer applies'.