Who's to say nothing good comes from a heated (nasty) debate?  Sure, a casual user doesn't want the comment section flooded with tripe, but to shut down a discussion may be picking and discarding fruit off the vine before it's ripe.<p>A solution to this might be rating comment <i>pairs.</i>  Any thread that becomes over-heated could be taken "offline" between the two users (or groups), possibly so far as scheduling a live chat if they're so passionate about their topic.  The (abbreviated) conversation would only re-appear in the thread (possibly by the readers choice) if the two came to a civil conclusion.<p>Granted, it sounds like a nightmare to implement, but I'd grant the Nobel Peace Prize to anyone who solved the online discussion conundrum.