If they paid, what is the issue? Life is full of reasonable risks.
No reason why not to trust the buyer. It might be a buyer and seller with multiple accounts and they simply have not had transactions on this account in the recent past.
Often sellers have a personal, private secondary account for purchases that they don't want others to know about. Keep in mind that your transactions (buying and selling) are not secret on eBay - anybody who knows you and your ID can easily view your transactions. Some people just have a second private account to keep the nosey people from snooping around.
If he paid what is your problem with him? Make sure the payment clears before you ship it. There is no way to restrict new buyers from bidding.
They paid you. What more do you want? SHIP NOW.
