I'm running a game right now where all Roles (and individual communication) is sent out via forum PMs local here. Scum group chat is (and speccy will be) done through chatzy - having never used it before, I didn't want to start 13 chatzy rooms and try to figure it out, so I'm doing such with just 1 or 2 rooms at the moment. So far, no issues. I can lock the room at night easy enough, and people have successfully written bold text. I have a setting selected to timestamp every message (although looking now, that appears useful day-of, and now it's just showing which day the message was sent for older messages).
However, I've never hosted a game on the forums here before (with QT), so I have nothing to compare to. I can say this is working. I don't know how well or how it compares to previous hosting experiences for people. We'll see how the next few hosts plan to approach it.