Here's something I thought was interesting:
http://www.imaginatorium.org/words/descend.htm To summarize, mixing kanji/kana and romaji causes some problems since kanji and kana are positioned in the middle of a square box, while romaji has stuff sprouting upwards or downwards (like the pole in "b" or "p"), therefore needing more height.
Quote:Now when it comes to forcing these two entirely different sets of principles into a single document, something has to give. And it seems to be the descender that lost out.
And so...
Let's see if we can find some other examples!