Admittedly this is a bit of a long shot...
My Jooma / K2 site: http://thumped.com
My XF forum: http://thumped.com/bbs
I'd like to unify the two and allow forum users to post comments on site articles. I'd used jfusion in the past for VB integration but it never really worked the way I wanted it to.
What I'm thinking is there'd be a comments forum, with 1 forum thread per-site article for comments on that article (i already have this bit automated via RSS posting), but what I don't have is the posts from these threads embedded as comments below the K2 article, or the ability to post to the thread from within the article page.
I can do a mockup if this isn't clear, but I think you probably know what I mean even without my crummy explanation.
Fully expect this thread to sink without trace. Like I said - a long shot.