I've bought from the seller in past. No monkey business on his part as far as I can tell from my experience.
Bids and retractions could be buyers trying to figure out where the current high bidders proxy bid max is set. I had a bidder try that with me once on a set of Bilsteins for my old Porsche. One bidder rapidly placed several bids up to my max bid and then retracted them quickly. I set a much higher max when I noticed that. Came to the end of the auction and they tried to snipe me, not realizing I had raised my max.