This blog post Why comments suck (and ideas on un-sucking them) has good advice among the hard talk. Sample:
One last thing: Stop making excuses. I know none of this is easy, but you really should have only one choice — either have comments and do them properly, or don’t offer comments at all. And if you’re offering them solely to increase page traffic to boost revenues, give up. Just quit. You’re hopeless.
It’s aimed at newspapers – who are still getting accustomed to the people formerly known as “the audience” – but you can apply it to any blog or community on the web.