I asked that question a while ago, and David Glenn from MS Typography told
me it had something to do with support for OpenType fonts. Seems two
"virtual" fonts are needed for two different OpenType layout tables (one for
horizontal and one -- the @font -- for vertical text).
If you google for "OpenType @Mincho", you should find the thread.
I never got rid completely of the @ fonts, though I de-installed all Asian
language support.
"@Arial Unicode MS" for example is still visible in "Tools > Options >
Compatibility > Font substitution" for any document.
But I think getting rid of the Asian language support (MS Office Tools > MS
Office Language Settings) got rid of most problems, which had caused me to
post.
Regards,
Klaus