It's not just Paul, but Linus also appears both in git and the kernel ;-)
You probably could register as these non-members with secret password, say "I'm this person" a few times, and then disable
... [More] the account for end-user log-in. When they actually join, they will find that "somebody else" claimed to be them, but I presume you already have a resolution procedure in place for such a case anyway, don't you? [Less]