I'm just not clear about the federation works I guess. If a power hungry mod (or maybe a good guy coming under very intense pressure from someone else) were to hate me, could he block me from sending messages to my friends by refusing federation somehow?

I dont want to be on a platform that can hold my friend hostage, is why I'm asking.

EDIT: If hub federation is needed for asynch messages, and unblockable (by hub owner) p2p used for chat when both users are online, then I guess that would be acceptable.