Yikes, we gotta get on improving Element and Matrix as a replacer ASAP. My apologies for shillery, I don't normally hock FOSS alternatives in the comments but I view this sort of offense by Discord as a militant action level of threat.
The feature none of them seem to have is creating a set of rules that users have to read and agree to before seeing the rest of the space, such is the case with Discord Community Channels.
I mean theres a shit ton missing for discord parity. I agree that matrix needs more of these features, just wanted to share a couple things that already exist