Thanks for the reply! To clarify, you mean to say that a single user-account can be the exact same entity on multiple teams? And so point-to-point communication is not affected by team boundaries?

What about server boundaries? Can they be federated somehow? Sorry if you are trying to answer this with your point about Matrix; I'm not familiar with it.

Edit: ah! Arathorn answered my question about federation. This is super cool stuff!