While I don't think that HN has hit this level yet, one solution that I've read about involved people who trolled or posted general nastiness. When people had reached a certain threshold or pissed off the wrong high-level mod, they got "ghosted". What this meant was that people who were "alive" or considered "living" could see "living" contributors' posts, but could not see "ghost" posts. Ghosts, however, could see other ghosts' posts, so they could, for what it was worth, writhe in their own debauchery and piss each other off, but not the pleasant and constructive members. I thought it was an interesting solution and apparently it worked very well.
Problem is it's not entirely clear what some people have done to get hellbanned sometimes.. I'm not sure what the requirements for getting it reversed are, either. I've seen some very constructive comments in that mess before..