Except, it's not a "user token", it's an address. It's as much a user token as a postal address or a telephone number is a "user token": not at all. It's a way

Except, it's not a "user token", it's an address. It's as much a user token as a postal address or a telephone number is a "user token": not at all. It's a way to contact a person, not a way to identify a person. Just because you can enforce that only one person with a given postal address can create an account with your service, doesn't make it an inherent "user token".