The combo of quick bans and incrementally earned rights seems to be a pretty effective combo.

I think user-driven flagging is starting to show its cracks here, though. I'm starting to see stuff flagged to dead status, from otherwise reputable posters, because they went against the current in a thread.

I really think HN should consider giving out limited mod points, like Slashdot did (does? haven't used it in 25 years.)

This would probably be the ideal* system for somewhere like Reddit, too.

* Defining "ideal" as what drives high quality discourse, not what drives engagement.