Reputation won't fix the problem.  A buyer with a stolen paypal account only needs to make one purchase to make a profit (he doesn't care about reputation).  It usually goes something like this:

1. Buyer with a stolen paypal account sends the payment
2. Seller sees the payment and sends the coins
3. The actual account owner sees the charge and contacts paypal to refund the charge
4. Paypal does a chargeback and takes the payment back from the seller

Now the paypal thief has the coins, while the seller is left with no payment and no coins.