D. J. Bernstein;
What Seng fails to do is compare IDNA to the status quo. Sure, the
status quo forces sites to stick to ASCII, which is visually unpleasant
for many users.
Though I, personally, can read, for example, Hangul (Korean Alphabet),
for almost all international users, it is much much more unpleasant to be
displayed a domain name in Hangul characters than be displayed Latin
character equivalent of it.
Though I, personally, can read many Chineses characters, for almost
all Japanese users, it is much much more unpleasant to be displayed
a domain name in Chinese characters than be displayed Latin character
equivalent of it. Note that Kanji characters of Japan is not Chinese
characters any more, just as Greek characters are not Latin characters.
So, even if your software can display Hangul and/or Chinese characters,
it does not make the situation better.
Masataka Ohta