Who are predictably downvoted!
I think the upvoting/downvoting mechanism by itself makes discussions unnecessarily competitive and hostile. Here's a crazy alternative: make the order of comments random and rotating. Of course you could still have flagging and moderation to remove bad comments, but otherwise get rid of the voting. You could still have nested conversations (though the UI for this is really bad on HN when the conversations become long), but the comments at each level would also be randomly ordered.
The theory is that the "best" comments rise to the top and the "worst" to the bottom. In reality, that rarely seems to be the case. It's typically a combination of popularity, controversy, accidental timing (some variation on "first!"), and the existence of replies to the comment.