I would say that if there is an accuser, then he must prove guilt, not the accused.

I've been looking at Gigabit's post history. In my opinion, it differs from the moment that, in the past, a person was an experienced miner and wrote quite lively posts; after a while, we see only general, dry posts about mining. I can say by myself: I am not a miner, and I don’t know all the subtleties, but I can successfully read any article and retell it in my own words. This happens in Gigabit posts after a break.

We communicate on the forum, and quite often people who have experience in this or that activity write on their own behalf. Gigabit never said he was a miner and knew all his secrets, although you can see completely different posts earlier.
But it is not worth relying on these cases to determine whether there was a hack or a change of account. Similarly, people are not required to keep their old wallets. Indeed, a lot of time has passed.
The bottom line is that even if Gigabit isn't the actual owner, it's pretty well disguised. I think there are a lot of such accounts on the forum; it's just that people don't treat them correctly.