Great idea.

I think friend/foe and trust signals should come from a user's voting. So I think it should operate transparently to the user and there should be a default shade-out option of bad actors, but with the option to view. So it's set-and-forget. On the backend - could you make it so if you've never visited HN before, and you install the plugin, the experience changes accordingly?

I had the idea to setup a forum somewhere else - this sort of functionality would come in handy as part of normal operation.