Is it possible to bid against myself?

No, if you are already the high bidder in an auction and you increase your maximum bid amount, the bid will not immediately change. As always, your bid will only increase in response to bids by other users, in the smallest increment possible to maintain your position as high bidder (up to your new maximum bid amount). The only exception is that in a Daily Auction, if your maximum bid is the first to meet or exceed the Reserve Price, our auction system will initially enter your bid in the smallest increment possible so that your bid meets the Reserve Price.