It's called "IntenseDebate" and it works like a charm.
All you have to do is put in a name, and anyone you want to ban disappears from your blog.
It's a breath of fresh air... unless you actually go back to your page in that program, you don't even know those on the banned list even exist.
It's awesome, it's free, and it works for Blogger and WordPress platforms.
It screens out the scummiest slime trying to drop a load on your doorstep.
You know... like Peggy Owens!
I recommend it!