@developing_agent Right but what I mean is that if you have an existing account on a server, and you have a streamlined flow (perhaps 1-click or even 0-click) for federated account registration, then you can easily end up in a situation where you accidentally create a new account instead of transferring the existing one (for example, if the client you're using is not logged in on the old one).
Email matching would provide one safeguard against that (on federated account registration attempt, the email collision would be detected, and you'd be prompted to take over the existing local account instead via password or, if you forgot, email verification flow).
