Ah, you mean for fediverse to work as an LDAP?
My point is Let’s imagine we have a board on some instance. You use your account on another instance to ask the owner of the board to give you access to the board. The contents of the board are, IMO in most cases of such boards, “members only”. So any changes happening inside should not be sent out to federating instances. Otherwise, privacy of such boards would be at the mercy of privacy of other instances. If restricted changes were sent out, technically speaking, any server it federates to can choose to show that content to everyone. Which means you won’t be able to access the contents via any other instance. Apart from the logging in part, you will still need to go to the instance hosting the board. Unless it would be for publicly accessible boards only, like codeberg issues. That use-case could work
Then how would they sell access in a deniable way?