Interesting essay. It's made me think about some things, and one of my in-progress fics is probably going to include some evidence of actual bisexuality now. Once Sokka gets old enough to care about that sort of thing. (Snogging Zuko and still flirting with the pretty girls. That's our Sokka.) (And by in-progress, I mean 'sequel to the in-progress one', because it occurs to me it'd be neater that way.)

May even use a bi label on the story just to see how people react.

Tangently related, but I've noticed that I give my Avatar characters a lot more diverse sexualities than my Transformer characters. With the Transformers, I just tend to stamp them as bisexual and move on. With Avatar OCs, I vary across a spectrum of firmly monosexual, mostly monosexual with exceptions, bisexual, and asexual.

I think either the genderlessness or gender disparity of Transformers actually discourages me from doing any serious exploration in varied sexualities with them.