He withdrawn his merit source role and he out from high paid campaign, if he want to sell his account, the two things I mentioned above would increase his account value. For me it doesn't make sense he sell his account with the current condition when he could make more.
Sorry but I think you are very optimistic and maybe a little bit unworldly if you think people care about that. This is not a religious principle, they don't commit a sin by doing that, so I don't think what you perceive as too immoral to be done is shared by other people. In addition a private key has never been an indisputable proof of identity or ownership, because it can be lost, stolen or given. Even for PGP there is a web of trust scheme, in order to address that.What if he transferred the ownership of private keys too? 
There's always any possibility, but talking about selling his wallet is too far IMO. That will affect the whole thing as sign a message is a solid proof to prove ownership or legitimacy.