I think federation is overrated. How difficult is it to have multiple accounts these days?
It will be very hard to vet users from other instances properly in the Fediverse. Even if tools exist to do better validation (like, for instance, allowing an instance to validate that the subscriber from another instance has a valid email address), someone with ill intent can figure out a way around that.
I think that the Fediverse could use an identity verification service, but fear that's what Facebook is trying to be.