[Theaetetus]

I'm guessing we agree about 95% of this, but re: "it doesn't take more time to display a string in Japanese than it does English":

1. It takes more time to detect a user's language than not to detect it. 2. It usually takes more time to render a page that can handle both LTR and RTL than one that does only LTR.

...and you can give many more such examples.

I don't disagree that basic proficiency is a more important cause of slow software.