Interesting... what about a progressive hellban, where there's a probability that the hellbanned user's participation is seen by others? The probability would exponentially decay after each offense and be slowly restored as a function of time without offense.
How about a ban that progressively hides the account from high karma users. In the first circle of hell, only 10k+ don't see the banned, second circle 5k+, etc
I think the other way around might actually be better. Newer, lower-karma users tend to be influenced by the comments they see; older, higher-karma users tend to be better about upholding the old HN values. If you make problematic users invisible to the old guard, newer users will grow to accept certain forms of behavior and even upvote it. If you make problematic users visible only to the old guard, they'll get better feedback.
