All bidders are effectively anonymous - if you look at the bidding history of any item, you will be able to see your own ID, and everyone else's will either be a code (like s****7) or it will say "Private Listing - bidder's identities protected".
The former, where bidder's names are coded, happens on all listings that aren't set to private by the seller, and other members would see your ID coded in the same way.
The latter, where all IDs are hidden completely from members other than the seller, is a listing specific option that only the seller can set up.
