Most sellers will not recognize if a bidder is a 
deputy service or not.  Even then, as long as the 
communication between the bidder and seller is in 
polite Japanese (and if the initial shipping 
address is in Japan, which it is most likely), I 
doubt a seller is Japan-o-centric enough to 
refuse the sale.

Besides, finalized auctions are usually 
considered a contract and the seller is obligated 
to complete the sale with the winning bidder.  If 
the seller cancels a bid before the auction is 
over (due to the seller not liking the bidder), 
then you lose nothing, right?