Vladimir Volovich <vvv@vvv.vsu.ru> writes:

> Well, i'm also not sure whether MIME officially registered some of
> Unicode encodings as allowable charsets for MIME parts, but if it is
> so, then yes, there is a single charset which includes all those
> languages, and much more. :-)

But we have to consider that messages should be possible to read,
shouldn't we?  :-)

I think a typical situation where you get a message with several
charsets is when you quote messages written by people who use other
charsets.  I don't know heads nor tails of Japanese, but if I respond
to a message from Katsumi Yamaoka / 山岡 克美 (who posted using
iso-2022-jp, and is likely not to be able to read Unicode replies),
I'd like to respond using iso-2022-jp.  And that I can do.