Only to other bidders. The seller and the bidder can see her name. Other bidders can't.
At one time they were.
Sometimes scammers would contact losing bidders and offer them a Second Chance, pretending to be the original seller.
Sometimes bidders in specialized categories would 'stalk' the bids of other collectors who were good at spotting bargains.
However, the new(ish) system leaves auctions open to shilling or more importantly, loss of confidence from bidders who don't understand how shilling* works.
*The shiller never wins. He makes the winner pay more than necessary.
