The account was inactive(no posts made) for six months prior to the suspected hack. And it has been an extra twelve months for a complain to be made. That must have been what attracted hackers to it, an inactive account is much easier to steal, without getting any rebuttals.

With a signed message it would be difficult to regain an account. But without it, and the suspected hacker having signed the account, it makes it more difficult.

The frequency of posts shot up this year, and also the change in language, I do not know if that is enough evidence on which to tag the account.
The mods and DTs would decide that. You can also leave a negative remark, just to serve as a detterent, and maybe use this thread as a reference.