By voting patterns, what do you mean? Features like how many times the user has voted in this thread/hour/day? How many times the comment has been voted, the replies have been voted, and the story has been voted? I didn't try those; maybe they'd work, but I have no intuition saying why they should.

Using ML to provide feedback is a bad idea. Most ML techniques latch on to surface features of the text rather than the deeper structure, so it'd just make it really easy for people to reword their mean comments ("this is just stupid" becomes "What an incoherent piece of gobblydegook" or something like this, which might make things funnier but I doubt it would help).