What I always hated:
You find a good topic, and basically ALL comments talk about something completly different.. and still get upvoted.
Maybe a thumps up for staying on topic?
Aha, that was the complete misuse of upvote and downvotes. The point was upvote what added to the conversation/topic and downvote off-topic/troll posts.
Instead they are used as the agree/disagree buttons, with people tending to vote with the majority.