I haven't used Discord too much, but my main gripe (apart from calling communities "servers") was that most communities had way too many channels already, but haven't seen them in action, so maybe that strategy works better in practice.
YMMV, I've been checking out discord and I don't really like threads much. It feels like the discussion is stashed away semi-hidden in a corner which sort of discourages casual / intermittent participation and you easily miss the whole thread. It's like I have to go out of my way and butt into someone's discussion whereas the chatter on an IRC channel feels open to every participant.
