Do you have examples of cases where vertical control has content? I thought there were no such cases known.
U+3031 and its voiced variant U+3032 are only appropriate to use in vertical layout. These two characters are AFAIK only used in Japanese, and the current recommendation is not to use them at all.
Unicode contains doubles of some CJK punctuation marks, one form for vertical layout and one for horizontal layout. It is inappropriate to use a vertical punctuation mark in horizontal writing, and vice versa. I wonder why this was not solved in the same way as with LTR/RTL, where some characters, e.g. parantheses, are mirrored when changing the reading direction. In CJK this is a matter of turning the characters 90 degrees.
Stefan
