I think it's naive to assume there's anything that happens on HN that isn't socially engineered in some way.

Sounds glib, but render down the actions and incentives of participation on the site. In a business-focused environment where there's opportunity to influence a large group, whether for direct commercial gain or reputation-building, competition will necessarily arise.

We're all socially engineering each other all the time.

Take away posting attribution and karma and it mightn't be that way, but those are big incentives for continued participation, once a person is invested. Could the site exist without them?