If you mean so that the seller doesn't see, you can't. But your username is disguised with an a***b alias (similar to but not the same alias as when you are bidding) to everyone other than you and the seller on the seller's profile. And everyone can see the feedback you left for others on YOUR feedback profile (which indicates that you haven't left any yet despite receiving 4 ratings from different sellers; if you only intend to leave negative or neutral feedback expect sellers who can check your feedback--like if you make a Best Offer--to decide if you are a good buyer to decide not to do business with you).
If you mean so that the seller doesn't see, you can't. But your username is disguised with an a***b alias (similar to but not the same alias as when you are bidding) to everyone other than you and the seller on the seller's profile. And everyone can see the feedback you left for others on YOUR feedback profile (which indicates that you haven't left any yet despite receiving 4 ratings from different sellers; if you only intend to leave negative or neutral feedback expect sellers who can check your feedback--like if you make a Best Offer--to decide if you are a good buyer to decide not to do business with you).
