I think one thing we really need is some decent moderation. This can come in teh form of staff, or by letting users do it.

I would implement something like Digg's bury system for articles, where you can vote a story (or argument in this case) for a list of specified reasons.

On this site, that would translate to things like logical fallacies. Like letting users tag arguments as Appeal to Authority or Strawman, etc.

That may lead to an unweildly number of tags though, unless you stick to a set list.

Another thing (or one that may work in tandem) is having debates that aren't moderated by the creator.

While in theory, this works nice and it helps the user feel they have more control over the direction of the debate, it generally becomes people banning users they don't like, or those who argue against their position. IOW, people let their personality get involved and act all butthurt. So I'm not sure about the self-moderation thing.

But who would moderate? and if we have tagged arguments, who is going to QC the tagging to ensure it isn't being done en masse or vengefully?

As far as the ratings go, just making an argument or a debate shouldn't count. Then it becomes a post-count type thing, and if you're a forumgoer, you'll know that post counts always become a highest-number game for some people (I'm looking at you, Joe & Kukla). Spam, iow.