After looking at the logs, I find it likely that this story is true, so it wasn't him personally who did the plagiarism. Trading accounts is strongly discouraged, but not against the rules. Therefore, the ban is removed.
And there you have it!
How do you feel about the idea of statutes of limitations on plagiarism cases? I think punishing somebody for a one-off offense done years ago (talking like 3 or more years ago) is a bit too stringent and the current plagiabot running around is a bit out of hand, leading to the banning of people for a mistake committed in 2014. Maybe the query or the rule should be tightened a bit. Just my opinion.