Downvotes are for comments which are not worthy of a response because they are not honest attempts at discussion.
They also did meta-moderation. You could choose to meta-moderate and you'd be shown a post (or posts) with their moderation and could select whether the moderation was appropriate or not. So a post like yours that got marked "off-topic" by someone (it's not, it's a fair and earnest question) would result in the moderator getting some kind of penalty in meta-moderation.
Another thing I liked was that if you participated in the discussion your moderation points disappeared. So if I moderated your comment (up or down) and then replied elsewhere, your comment lost or gained a point.
That's wishful thinking. In practice that's just what it is. I'd be in favor of some magical gui change that would fix that, but it doesn't exist.