Looking through his feedback a couple of things pop out. He seems to source his sales material from
ebay sellers such as NYStamps and Matthijs_Philatelie. One account has thousands of such feedbacks, 2,688 out of 3,369 to be exact. Perhaps he wants to keep separate ID's for bidding and selling although the two do mix a bit. I did also notice that he purchases from a now dormant (temporarily?) seller, Chesirecat-0, that rings a bell as an unsavory seller (cartel?). It would make sense that he might want to hide his material sources from inquisitive bidders. All conjecture.