Writing trans characters in Honor Bound and future projects

A year ago I slipped and accidentally wrote a huge post elsewhere about how I wrote trans characters in Honor Bound. Then I wrote this up and never posted it. Here's an expanded and edited version. I'm coming to this with a focus on long-form interactive fiction with customisable player characters, of the kind that I publish with Choice of Games, but it's applicable to other kinds of narrative game too, or worldbuilding in general. Marked vs. unmarked gender and transnessFor my games before Honor Bound, I treated nonbinary PCs' and NPCs' gender as unmarked because I wanted to demonstrate that gender and being nonbinary wasn't a big deal. I still think that's a decent way of doing it; for me it helps show that a setting isn't sexist, homophobic, or transphobic. But while I allowed players to choose pronouns and enter custom ones, I didn't allow players to state that their PC was trans. Sure, they can headcanon, and I never write assuming that a PC is cis. I've had wonderful feedback…