Especially in light of recent changes to comment flagging so that now we distinguish between comments that are chatty, flagged for general reasons, or are rude/offensive, could we have some sort of heuristic that bans people from leaving comments if they have too many comments correctly flagged as rude/offensive?
Restoring the user's ability to comment could be done via having them contribute more answers. Answers are not the same as comments of course, but that's a pretty decent way to track someone's positive contribution to the site.
Alternatively, the ban could be time-based and just put the user in an automatic timeout for a few days with an appropriate message that'd let them know that too many of their comments have been deemed rude or offensive by the community.
Note: I'm thinking just about rude and offensive comments here. Comments flagged as "chatty" or "general" would be not count.