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.
Definitely a hacker or well someone who bought the hacked passwords. Check out all these accounts and their last active:
They were all last active on Feb 19th, but dormant before that. There is probably more breached accounts but I don't feel like looking right now.
Looks like the hacker had the same thought I had; Satoshi possibly created a new account either right before he last signed off or shortly after. The hacker was probably looking for a PM or email address that would lead to Satoshi or just some kind of clue.