[That_Guy]
Generally speaking, when a pairing is presented the shorter of the two is presumed to be the submissive. This is a stereotype following that most girls are shorter then guys, and to be more feminine is to be shorter. It's obviously not a concrete rule, and has little significance when judging people outside the yaoi arena.
Ahh, so that's why I'm not feminine! Well, that was random...
But height usually doesn't matter in a yaoi relationship, but it does help establish who the uke is and who the seme is.
