The piece I feel would be useful is a simple link that is auto-generated from every hacker news discussion. You could hit it by going to the site from a comment link, for example: http://blah.salon/ and it would determine based on your referral URL what post you're talking about, then let people do some sort of collaboration around it.

Think of the "AMA" thread posted by the Angel investor yesterday (i think his name was Josh).

It would be cool if you could place a simple link there which would take you to a page full of discussion points, videos, etc that people put together. Or maybe just collaborate in a different fashion than text comments?

Anyway just an idea.