The chargen app serial number is part of the what goes into the unique ID, along with the character's creation date. Even if someone used a copy of the chargen app downloaded elsewhere and not reserialized/only ever used offline without getting an update, they would have to hit "save" at the same instant to as precisely as the system clock records it as someone else doing the same, with the exact same character data, for them to get a false positive. Because the universe is contrary I'd therefore expect it to happen within a week while some prominent uSpud is reviewing the new game, but happening twice without someone specifically trying should be hard. It's not a feature that would be advertised to make that into a challenge, either.
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‎noli esse culus
‎noli esse culus