Exactly! And really, we already have a flagging system: the downvote. My understanding is that comments on HN should only really be downvoted for the same rea

Exactly! And really, we already have a flagging system: the downvote. My understanding is that comments on HN should only really be downvoted for the same reasons as pending comments would not be approved. So why not improve on that existing system? When a comment is downvoted, it should ask the reason for the 'flag', with choices representing the various commenting rules. This should help ensure that people are using downvotes correctly, which should allow them to be acted on more strongly. Sufficient downvotes (or sufficient downvotes with the same reason) could hide the comment entirely.