eBay will reimburse seller fees as long as they don't have to get involved in the return (i.e. you refund the buyer in the allotted two days after you receive the return), if eBay has to get involved they keep the fees and the seller has to cover the difference. The reimbursement will go to the buyer, not to you. Your part of the buyer's refund will be the amount you received after seller fees plus shipping (if applicable) plus return shipping if the return is a not as described return (if it's a remorse return sellers can require the buyer to pay return shipping).
F.Y.I.: eBay will put your funds on hold if a buyer opens a return until the amount of the return is covered. The funds that are put on hold can only be used by eBay to refund the buyer if they have to get involved, you can't use the held funds to refund your buyer. Your refund will come from either your available funds (if you have enough to cover it) or your backup payment method. After you refund the buyer eBay will then release the funds they put on hold and you'll receive them in your next payout.
