It isn't really a discussion list so much as people sending important announcements or sometimes sending posts asking a question, soliciting private answers, then compiling and potentially anonymizing the results before posting a consolidated response a few days later -- super efficient.
Per batch email, group discussion (FB mostly, for us), group chat, etc usually involves a subset, or direct asks of other groups. I personally know nothing about consumer stuff, so no one ever asks me for CSS advice, but plenty of times hosting, security, etc questions come up.
Plus the purely social stuff is usually with a self selected subset; YC is diverse in interests. There is even basically a YC gun club, and a bunch of YC anti-gun activists, coexisting peacefully :)
