The people on yahoo are all-around more anal-
retentive than the average ebay seller.
Many sellers will not let you bid if you have no 
positive feeback. I ask you, how are you supposed 
to get positive feedback if no one lets you make 
a first purchase? 
It is a general trend that sellers do not want to 
ship overseas. It is very rare to find one that 
does, regardless of what they are selling (I have 
spent a lot of time looking there at manga, and 
such.)
Although I agree that refusing to allow you to 
opperate through a middleman in Japan does sound 
discriminatory.