Slashdot is an interesting place to meet with fellow avid computer users, and share stories and comments of a social fraternal nature. It is not the place for deep thoughts... nor can it be due to its very nature. There are a number of possible moderation signals to give, insightful and funny being amongst them, but in the end it all comes down to points.
Funny, insightful, informative, troll, and other signals should be orthogonal to each other. It should be possible with the default UI to filter out funny messages, as they are often off topic, and distracting. Sometimes that's all you want. Because it all comes down to points, all of that information is lost, and every comment is essentially an entry in a popularity contest.
Information is lost in the moderation system, and further information is lost in the hard limits up or down... nothing can ever go higher than +5 points, or below -1. This means that a really popular story may have more than the default 50 replies shown reaching the +5 level of moderation... which cancels out the effect of moderation for those entries.
It would be an interesting exercise to redesign the moderation rules to accomodate tags or user-supplied dimensions of rating, such as "accurate", "bogus", "spam", etc, which I leave as an exercise to the reader.