Wow. The level of detail in this is something that for English I think
you'd need to look in sources like Hart's Rules and the Chicago Manual
of Style just to begin to compile. AFAIK there is no W3C document
covering Latin or any other script that goes into anywhere near this
level of detail about things I suspect only very experienced compositors
or copy editors would usually know.
I don't know anything about Japanese text layout so I can't comment on
the details - but I think it is very useful for non-Japanese speaking
developers to have this kind of detailed information about Japanese text
formatting available in English so they can design applications to
accommodate these requirements.
Are there any plans for W3C to prepare this sort of document for other
non-Latin writing systems?