I know this was declined years ago in this old feature request, but my feature request is actually pretty different. The main purpose of my idea is to collect more signal about comments that would allow to automatically hide comments that aren't useful without deleting them.
Comment flags work pretty well for offensive comments, those are often quickly removed. They don't work as well for anything else, it is unlikely that enough users flag for one of the other reasons that the comment will be automatically removed. I strongly suspect that almost all obsolete, too chatty, ... comment flags are handled by diamond moderators. The problem with this is that it doesn't scale well.
Downvoting would be a process with much less friction than flagging, you don't have to select a reason from a list like for comment flags. Downvoting takes only one click, while flagging comments takes three. Flagging is also generally associated with more serious issues.
Some details on how downvoting would work exactly:
- no reputation penalty for anyone
- comment score = upvotes - downvotes
- comment score below 0 would not be shown
- comments below a certain negative score would not be shown by default
Flagging would then be mostly for offensive comments, not for general cleanup. Downvoting would make it relatively easy to hide comments that are simply not that useful, without actually deleting them.
I'm not sure what the best method of hiding comments is. The simplest option would be to use the existing hiding functionality. Another option would be to hide them even a click further behind the "show x more comments", at least if there are many comments on that post.
Previous attempts at hiding comments automatically failed mostly because they did hide too many good comments as well. The existence of downvotes might provide enough signal to make another, better attempt at hiding comments automatically.