Looking at the current comment privileges page, and reflecting on the effort that must go into dealing with comment flags, I wonder whether we could use the Badge system to encourage people to tidy up their own comments, rather than rely on moderators to find and delete comments which no longer serve the community.
We already have the commentator and pundit badges to encourage people to use the comment system, but I wonder if a Boy Scout tag or something similar might be appropriate to encourage the deletion of obsolete comments.
Just as the Boy Scout Rule says "Always leave the camp ground cleaner than you found it", this badge would be granted for deleting (tidying up) say 10 comments.
In accordance with the Positive Badge Rule, this might encourage people to get into the habit of tidying up their comments when appropriate.
Related to Need a way to clean up obsolete comments.