> Second, how much of the passport information do you hash that it's not reversible?

That doesn't even matter. You could hash the whole passport and the passport could contain a UUID and the hash db would still be usable to correlate identities with accounts, because the attacker could separately have the victim's complete passport info. Which is increasingly likely the more sites try to use passports like this, because some won't hash them or will get breached sufficiently that the attackers can capture passport info before it gets hashed and then there will be public databases with everybody's complete passport info.