I don't know if this is still possible, but I remember years ago placing two proxy bids at the same amount (perhaps before I discovered sniping, don't remember).
This was to discourage someone from bidding on the item so I would get it for a small amount. Someone would see 2 bids, figure my second bid was higher, and not bid. Of course, if they decided to nibble it wouldn't work, but I wasn't willing to pay more than a small amount anyway. Sometimes I won, sometimes I didn't. I have no idea how many times I "scared someone off", if ever.
Maybe this is what the seller is po'd about.