While discussions of what goes on in the bathroom may make most Americans uncomfortable, it certainly isn't so taboo as to point out a different toilet. Perhaps the Japanese culture is different, such that, while people may have wanted to ask why you have a fringe toilet, social norms kept them from doing so.
I'm not Japanese, nor have I spent any time in Japan, so that's purely conjecture, but, knowing what little I know about Japanese culture, that wouldn't strike me as beyond belief.
You're right, Japan has a long and very interesting obsession with poop, primarily due to their geography.
Japan is a series of volcanic islands with, historically, a very limited indigenous supply of large poop producing creatures like like cows, horses, and pigs. The result is that there was a great scarcity of fertile soil. To supplement their soil they instead relied on human feces. So valuable was it that back in the day you could sell your poop to professional manure collectors who walked around town with large pots.
The cultural legacy extends well beyond toilets. You may have seen recent articles about people creating meat from poop, and poop powered motorcycles. It's no coincide that those are Japanese inventions. Funny how a thing like geography affects things.
Speaking on cultural differences and American willingness to discuss bathroom culture...
I, personally, don't like the idea of a warm seat. All I'll be thinking about is "someone else just used this toilet".
Maybe one day I'll use one and it'll change my outlook completely, like the George Foreman grill nudged my outlook on the validity of infomercial products. But, until that happens? Nope, no thanks.
Well, it is still more economical to warm up ONLY the seat than insulating the whole room. Especially since you do not stay hours every day in the restroom.
I'm not Japanese, nor have I spent any time in Japan, so that's purely conjecture, but, knowing what little I know about Japanese culture, that wouldn't strike me as beyond belief.