Here's a situation I run across quite often:
- Joe posts an answer that contains an error.
- Jane posts a comment, pointing out the error.
- Joe is nowhere to be seen for quite some time. Jane's comment gains a dozen upvotes.
- Eventually Joe returns and fixes the error.
- Jane's comment stays there for all eternity.
At best, Jane's comment is now pure noise. At worst, it is noise that is extremely confusing, especially to unexperienced users. ("I have no idea what she's talking about... but so many people upvoted her... am I drunk or what?")
Obviously, we can't expect moderators to constantly sift through all comments. Obviously, normal users hesitate to flag highly-upvoted comments as noise (this is more of a problem on beta SE sites, where many users don't really understand flagging, or are scared off by the stern question "Really flag this as noise, offensive, or spam?"). Obviously, Jane could delete the comment herself, but she is probably aiming for the "Pundit" badge.
Suggestion: in order to reduce noise and counterbalance the "Pundit" badge, we could introduce a badge for deleting X own comments with at least Y upvotes each, in a spirit similar to that of the "Disciplined" badge.