Use Reddit! Create a public/private subreddit (whatever suits you). It's a perfect place for discussions, and you can use IFTTT to provide you with webhooks.
Reddit is terrible for discussions. It is perfect for current, forgotten-tomorrow consumation of things.
Reddit isn't perfect, but it's much less intrusive than facebook and people can search for past discussions. I know it is a low bar, but then I don't have to worry about spams, registrations, etc. Plus, if I don't have time to read/deal with it today, the discussion and the person isn't gone tomorrow which chat services tend to do.