The vote counting thing can be interesting.

There's the classic "I wish facebook had a dislike button" or the equivalent for twitter.

But in the thread-based forum context, removing the downvote has interesting effects. For one, it stops people who down-vote-brigade to lower visibility. It also stops the "I don't like that guy" engagement and works on a more positive "I appreciated this comment" mode.

It's not one-size fits all but I've seen positive effects on more marginalized forums.