AFAIK, nothing was permanently or irrevocably deleted. From all the public statements at the time, all that happened were the accounts were suspended.They would then need to reach out via the recovery link to prove they were really a person (and not say, a bot). (I'm just going off public statements here).

In terms of handling and deleting user data, I do know we have some pretty clear guidelines around this - user data is sacrosanct. You can read up in the ToS, or if you need specific guidance around your personal circumstances, I would always encourage you to consult a legal professional.