Maybe what HN needs, could be some way of giving people who want the heated discussion, a way to express these seperate from rest. Maybe a tab that shows controversial comments, so you can switch between the "calm" and the "heated" discussions.
Most of these problems aren't a big deal on a case by case basis because, really, what's the harm of one more google vs microsoft flamewar in the scheme of things. But they're a problem in the example they set to other users, especially newer users who are still malleable. They'll write better comments if they think that this is a forum for good comments. At least that's the philosophy.
I like this idea. I'd say all who are hellbanned should see other hellbanned users' and they can nuke each other from the orbit in their own little sandbox.