I don't know if it shows who's actively typing (from what I saw from the discussion thread I don't think it does), but I found an addon that would update threads in real time without having to refresh the page.
Live Content by Xon (Goated XenForo creator by the way).
I guess I could ask the .gg admins and ask them directly how they have it sat up; sometimes site owners are cagey with the addons they use (even if they're not custom), so I don't know if they'd be willing to tell me directly, but I don't know until I ask I suppose.
If anyone else has any idea how they might have it set up I'd be interested in knowing. I think it'd be cool.