If you find/start that forum, I'd join. I think there is more than enough room on the internet for HN and a site/community like the one you're describing. I've learned more from HN than I have from almost any other single source, and I would love to find more communities with that same/better level of discussion.
Are there any other places you've found that come close to what you're looking for?
I've had terrible experiences with the usability of ning. It could always just be a private invite only forum. Email me and lets chat more? Email is in my profile.
Are there any other places you've found that come close to what you're looking for?