Quoting a mail I received:

There is an other missing feature (I think it is missing but I may be
wrong) for good Japanese text support called tatenakayoko (縦中横). I did
not find any description of it in English (though I did not search
that much) but it is quite simple. The meaning can be guessed from the
characters : 縦 "tate" here means "vertical", 中 "naka" here means "in,
inside", 横 "yoko" means "horizontal". It in fact just consists of
putting horizontal text in vertical text. And when I say horizontal
text I do not mean just a character, but generally something like 2 to
4 characters (but half-width one, not full-width), most of the time
numbers (especially in addresses) or acronyms.
Here are a few examples (the text around the images is in Japanese but
it is not very important):
http://www.japanlink.co.jp/dtpjiten/ta/tatenakayoko.html
http://www.sophia-it.com/content/縦中横
Like most features particular to Japanese (like vertical writing,
rubi/ruby/furigana), it is the kind of features available only on
special Japanese versions of Word, InDesign...