To protect bidders from fraud, information about a user is made anonymous during bidding. Bidders can see their own information, but cannot see information related to other users during the life of the auction listing. When an auction listing ends with a winning bidder, the user ID of the high bidder is exposed.
During the duration of the auction listing, the UserAnonymized boolean field will be returned to an active bidder as 'false' in the container that applies to that active bidder, and 'false' to the seller of the listing for all active bidders. The UserAnonymized boolean field will be returned to as 'true' to everyone else for all active bidders.
Response fields are made "anonymous" in different ways. Some fields may not be returned at all, while other fields may be returned, but with masked or dummy values. For example, the UserID value may look like this: "2***3".
Anonymous fields are explained in more detail in call reference documentation.