The way PG controls comments here is with the up-vote down-vote ranking. It works in separating the article discussions from the opinion oriented posts. Without the ranking the opinions mix with the article oriented posts, creates a sloppy discussion board. Another approach is not to bump opinion posts downward but horizontal into a new list of posts where you expect the posts to be bumpy at best and offtrack of the original topic. On the opinion list, confrontational posts are upvoted, 5 strikes and your out for a month.