I've done some business with monbux in the past (both Paypal and Interac transfer).

I can easily confirm if he is the original monbux or not.

I still have his banking info saved in my banking portal.

I could send him a small transfer (few dollars) and if he is the original monbux, he can easily tell me this amount.

If the monbux forum account is bought, then of course the new owner would not have access to the original monbux's bank account.