Why is it so important that we know how tall or short either one of the romantic leads is in a yaoi fic? Why are some authors compelled to put in such indicators as the word "up", as in, "he looked up into his eyes"?
Even worse, why do some fanauthors go to the lengths of flaunting canon to make the uke shorter than the seme? Such is the case with Cid and Vincent in FF7-- canonically, Vincent is four inches taller than Cid (according to the game manual), but since he's the uke in that fan-created pairing, he must be depicted as shorter!
Unless it is an absolute necessity (when describing children or certain types of animals, for instance), height is, IMHO, one of those factors that should be left up to the imagination. It's a holdover from fiction with het pairings and general gender stereotypes where men are typically taller than women. The height thingie in yaoi is just another seme/uke device, that subconsciously feminizes the latter half.
Just my thoughts...
(cross-posted to yaoi_rants; apologies if you're seeing this twice)