Why not just create a thread in reputation and announce if you will leave the forum? in case you want to comeback, you need to sign a message from your old address. I think these two things are enough to prove someone ownership.
This should be a fairly effective way to notify members here that your account is retired. As several people did, just like Lauda did before and it really worked until now the account is safe.
Lauda ProfileBy making or creating a post of goodbye BitcoinTalk forum:
https://bitcointalk.org/index.php?topic=5282911.msg55407286#msg55407286Make a statement on the related reputation about "PGP-key compromised and revoked."
https://bitcointalk.org/index.php?topic=1159946.msg55407295#msg55407295And even it's needed, Neutral flag given.
Or asking for account banned.
Maybe that could be an example of terminating an account on this forum and making it safe in the future from various hackers or AI or something like that.
But exactly, if this is needed to do it. Because now, there is 2fa protection available to be used. But, if this really needed, someone can do it to prevent more.