Where's the signed message?
He didn't have access anymore.
I don't really feel the need to justify me here, however:
The posting habit changed dramatically
The language changed
The original owner (alleged if you prefer) never asked me to do this
It came to my knowledge only after someone else asked him if he was really new here, because of all he knew.
Also the new user didn't care about me tagging him. All of this together makes it very unlikely he is lying, and it should be fairly easy to the owner to speak french again, if the account didn't change hands.
If he has an explication of some sort I might reconsider of course.