Discord is also rolling out an age inference model that analyzes metadata like the types of games a user plays, their activity on Discord, and behavioral signals like signs of working hours or the amount of time they spend on Discord.
“If we have a high confidence that they are an adult, they will not have to go through the other age verification flows,”
Seriously though, unless you have positively identified the person who created the account in the first place, you have 0% chance of knowing whether it is the same person using it today.
Gamers sell their high-level accounts all the time. It would be a simple matter of economics that the Discord users with the oldest accounts sell them to 12-year-olds. Likewise, accounts are shared willy-nilly, whether or not that violates the rules. And accounts can be stolen or compromised, if you're really hard up.
Of course this won't be 100% effective, maybe 80-90% effective. That's all they need and expect from this system.
HN is constantly obsessed with is it perfectly effective?
No law, none, is perfectly effective. Speed limits certainly aren’t self enforcing, but remove your neighborhood’s speed limits first if you truly believe laws must be demonstrated perfect.
If transfer of accounts is a policy violation, then Discord has legal cover to confidently assert that, once ID is verified, the ID'd person is the owner and controller of the account thereafter.
Account selling, stealing, and sharing will certainly still happen, but that's grounds for banning, and not Discord's legal liability anymore.