I have no idea. My usual trick is to go by language and to look at names, but - not so much in this case! (if you have links to any of the discussions mentioned above, I'd love to see them - I only dip my toes in anime fandom, and I can find the infrastructure kind of impenetrable.)

As far as the blue-eyed or whatever Japanese people, I wonder if it's actually not more like western characters with purple eyes or green hair or whatnot - sexy exotic impossible characters, you know? But none of us are going to see a heroine with purple eyes and conclude that she must not be caucasian. We're just not always good at extending the same imaginatve freedom to other cultures/ethnicities.