... on the other hand, Slashdot's moderation system is awesome for both efficiency and accuracy.
At any given time, around 10% of active users, people who log in and post at least occasionally, are gifted with moderation points, usually 15 at a time. Those users are deputized as moderators. They can choose to add one of a half-dozen positive moderations to a comment (Insightful, Funny, Informative etc.) or one of a couple negative mods (Off-Topic, Flamebait). If they post in a thread where they moderated, their moderations are un-done. Users only get to keep their mod points for three days. They can't be hoarded.
That means that good stuff rises to the top and the more active a discussion is, the more the readership will flag comments as worthwhile.
Users with a history of positive moderations get a bonus point applied to their comment automatically. Users with a poor history have a -1 or -2 comment rank applied so that their comments are simply invisible to the majority of Slashdot users.
Any user can also elect to Meta-moderate, examining a few random comments that have had moderation applied and opining as to the fairness or correctness of that moderation. This means that someone posting an unpopular but possibly valid opinion has a recourse that's controlled by the user base, not just site admins.
The end result is that Slashdot has a very high signal to noise ratio. It still has tons of trolls, but it's very easy to filter and get a lot of good information in the discussions.
Anyway, yeah, comment ranking can work if the people who set it up aren't morons.
I don't have any interest in the comments on the comments.
