So if I claim fubo
as a username on Signal, that means what? Nobody else can use that username? If so, it's another global namespace, same as Twitter; ten or twenty years in the future, someone's gonna want to be reclaiming disused usernames.
(What if I want to be fubo
to some people, and MissCatPictures
to other people? Can I do that from one phone? One phone number?)