In regard to the point that Hal had activity on the Bitcointalk forums after he died, see this post by an admin:

Bitcointalk link

I kept his account unlocked because I thought his family members might want to look at his PMs or something, but this is looking like his account was almost certainly compromised. So I locked his account. The person who controls his account gained access via email-password-reset, so his email is probably also compromised.

Additionally, here are the two posts that were made from his account in 2017. I really don't think Hal would say "I am risen"....

Segwit needs to be activated. I am risen.

For the record, I do not support anything that Jihan or "Crooked" Roger are doing with BU.

It's fun to speculate that Hal was Satoshi but I think it's equally or more likely that Satoshi willingly vanished from Bitcoin in order to keep it in line with his "vision" - completely decentralized (no figurehead). Though I suppose that's a different debate entirely.