IIRC, ID3v2 allows labelling of encodings - I guess emptool and emplode probably ignore these and assume ISO-8859.1 instead...
ID3v2 supports 8859-1, UTF-16, and (in v2.4.0) UTF-8.
Currently, emptool/emplode ignore UTF-16 and UTF-8 tags -- not that there's much else we can do, with only 8859-1 fonts on the player. This is, of course, a Bad Thing for those who want their songs labelled in Cyrillic, Hebrew, Welsh etc, let alone ideographic languages, but other car-player work has just always had higher priority.
We might do something with Unicode tags for some future car-player release (with UTF-8 on the player), but it won't be in 2.0.
Peter