And the proof for that claim on his trust page would be what?
Because he just posted the addresses on the staking page and not signed a message with it? Really?
There's a few links on his page but the evidences are not exactly concrete.
I would go with innocent until proven guilty and there isn't any evidence that the account sale wasn't clean so I suggest we treat the account sale as a separate issue because they aren't really related. I doubt this is related to that account sale.
Anyways, I don't think OP's issue is with the database leak or any inactivity. I vaguely recall that an explanation about the inactivity would accompany the ban message.
OP, if your account was locked, it must be for a good reason. I doubt they would exempt you from that proof of ownership unless it's under some special circumstances, especially since I would suggest you to try to find the relevant private keys since Bitcointalk's IP logging policy would probably have removed the IPs you used from years ago by now.