It was already requested by users to block Hal Finneys account. Let's not forget that this forum suffered from a massive hack and the passwords got bought in the dark web I think.
I don't it would be a hacker.Had it been one of the attacks due to password breaches,theymos would block the account instantly and or change the details so hacker couldn't use it anymore.
Worst case scenario,Hal's son would have contacted theymos privately and on certain conditions would have gained access back to his Father's account which is completely normal.