I doubt this is the case with them... I see 
foreigners in their store, and they don't seem to 
mind deputies bidding on their auctions either
(knowingly that they're dealing with a deputy 
service).  Maybe it has something to do with how 
you asked the question?  Did you use Japanese? 
English? Romaji? If you asked in English or 
Romaji, most likely won't be getting an answer 
then.