I understand your point, but for a long time the tougher nut to crack for online forums has been quality, staying on topic, and not derailing the discussion by being uncivil or hostile.

One of the nice things about HN is that users are rather blunt in their critiques. I think the gatekeepers (>1k karma) will generaly do a good job separating frankness from hostility.

At any rate, it's an interesting experiment and I'm truly curious to see how it plays out.