This was a difficult question that made me really ponder it, and I'm not glad you asked it. But I felt obligated, as 50% of the Room Controller Brain Trust here to answer.
A transexual wants to play on gor- what do they do?
My advice would be to find a realm where they would be more welcome. They can't control how other people will be impacted, and it just would be better for everybody if the transgender person roleplayed somewhere where nobody cared about true gender.
As an RC, if someone approached me about this, I would have to rule that a transgender person would have to play their true gender. If they changed their gender, that's what their gender is, and that's what they have to play.
I could understand it if they wanted to play their previous gender, for nostalgia's sake, or whatever. They might be very good at it, but I would rule that to be gender-bending.
Somebody in transition, I would ask them not to play at all until they were absolutely positive beyond any shadow of a doubt they were not going back. If they insisted they had a right to play, I would probably acknowledge that, and tell them to play the gender they are becoming. But if they were not good at it, I'd kick them out.
I don't feel good about that last part, because I would like to let them learn to be their right gender. But not at the expense of other people.