I have the same problem with Kanji (Japanese use of Chinese characters), Hiragana and others.
It breaks some themes. Especially "magazine" style ones which dependent on automatic extracts.
Part of the problem is that authors/languages do not use word spacing, and so WP cannot word count. I guess also WP allows but does not recognize oriental punctuation marks.
At the very least, could there be an option/extension to 'Kanji' count?
Unfortunately, it is even harder, to impossible, to programme users to know, understand, and use the <more> tag. Therefore, we really need a technological solution.
I cannot speak Chinese or Japanese and so do not know the the native WP support website say, nor how they have address this problem. Can you, or someone translate?
What are you using to do the multi-national/multi-lingual translation?
I loved Jlanguage extension but it seems to have died ... http://jakobj.dk/blog/archives/43.
I wish there was more attention on multi-lingual blog sites/development. I see them as key in international community building.
Thanks.