Slashdot's comment moderation system is one of those wisdom of crowds things that are periodically held up as exemplars; community feedback, allowing the best to bubble to the top and so on. People who actually read Slashdot comments, even only showing high scoring ones, may be aware that it doesn't necessarily work this way.

One of the reasons for this is that Slashdot's '+1 Funny' moderation option tacitly encourages off-topic comments, because it encourages people to be funny even if there is nothing to their comment besides humour. As a result, an appreciable amount of the high-moderated comments on any random story are merely random humour.

The moral here is that people do what you reward them for, so be very careful what you reward them for. Especially in communities, where there is public feedback that amplifies those rewards.

As an occasional moderator, I also have to say that Slashdot's comment moderation interface is not great for its intended goal. The view of comments that I really want is 'most recent comments first, only for comments below a rating threshold', because this is what I want to pick out missing gems. (A comment that is already high-rated probably doesn't need me boosting it further.)