Just few months before he started plagiarizing he was talking about it in his self-congratulatory post, meaning he knew what he was doing and what were the consequences of his action but he went with it anyway. Imho, in his case signature ban could be enough, but not to go without consequences like he did.
Did he plagiarize after the post you quoted? That means it was not an unintentional mistake. I don't think there should be any form of exception in such case. Mistakes are common, people barely read the forum rules. But if someone knowingly plagiarize, mod must ban them IMO. Exception should be for people with mistakes only.