Because it was brought up on the voting post and is something I was planning to essay on sooner or later, anyway.
As stated in the app, Nuriko starts off (and spends half of) the series crossdressing. He has been crossdressing since he was ten (when Kourin died) and according to Yukiyasha Den, this is how he ended up in Hotohori's royal harem. He is in love with the Emperor, and when he finds out that Hotohori is interested in Miaka, he proceeds to spend all of his time making Miaka's life living hell.
Eventually, they both become good friends and later on, when Miaka finds out about Nuriko's secret and freaks out, he easily says that he has "abandoned the path of manhood for the sake of love," and that gender is irrelevant to him. It's also around this time that the 'okama' joke starts running (people calling him gay/crossdresser and Nuriko spazzing and yelling in return).
As the series progresses, we see how Hotohori continues to be stupidly in love with Miaka and how Nuriko starts resigning himself to the fact that he will never be able to be with the Emperor.
Blah, blah, more stuff happens and when Miaka and the other Seishi are on their way to Houkan, their ship is attacked by Soi, which causes Miaka, Tamahome and Nuriko to almost drown in the middle of a storm. It's while they're waiting to be rescued that Nuriko tells them Kourin's story and the reason why he crossdresses and he also says that finally, he feels like he can let go of Kourin's memory and start acting like himself.
From this point on, Nuriko starts crushing on Miaka and this is where my head starts to hurt.
TANGENT! I was originally planning to app Nuriko from before he cuts his hair, because I am a whore for his braid his sexual preferences become a mess of sorts after that. But as I was rewatching the series, I understood this would only make stuff more complicated for me and that I wasn't allowed to dismiss such an important character-defining event just because I was lazy and didn't like what Watase did to her character.
Anyway, back to the story. There are two important conversations that I quote here because I consider them very relevant and because they more or less explain how Nuriko himself feels in regards to his sexual preferences after the haircut.
The first one takes place after Miaka and Nuriko have been attacked by Ashitare for the very first time. Miaka comments on how Nuriko has been acting a lot like a man and Nuriko replies that it's all because he cut his hair.
Miaka: But then, you don't want to be a woman any more and get Hotohori to love you, right?
Nuriko: Hey, that's right! I want Hotohori-sama to havet he greatest happiness possible for any man to have. But, is there any woman who's as brilliant and beautiful, loyal and loving as me? You can't find anyone like that anymore.
Miaka: ...I knew you hadn't really changed.
And the second conversation is from when Tamahome and Nuriko are chatting at the bar, after Nuriko tells him he should be more careful with Miaka and their relationship, because he just may want to steal her from him.
Tamahome: You? Forget it. I thought you preferred Hotohori-sama and were determined to make him love you.
Nuriko: That's the female part of me.
Nuriko: It's strange. I wonder why cutting your hair would make you feel so different.
Nuriko: Earlier today, I was ready to give up my life to save Miaka. Ever since I cut my hair, I have discovered that I definitely felt more and more like a man. What happened, was that today, for the first time, I realized that. And as a man, I think I would have loved Miaka.
What I see, from these two conversations, is that even though Nuriko has finally given up on crossdressing and acting like a girl, his feelings for the people he loves remain the same. A lot of people claim that after the haircut, Nuriko 'stops being gay' and I strongly disagree with this. First, because Nuriko has never been someone who falls in love with people based solely on their gender; and second, because he himself talks about "the female side of me." Also, if the interwebs doesn't lie, Watase herself has stated Nuriko is bisexual, so there.
So basically, the way I see and plan on playing him, is as bisexual and with nearly zero gender qualms. No, he won't be frolicking around camp in a dress (unless it's a special ocassion 8D), but things like his flouncey-ness and narcissism, among others, are parts of his personality I don't want to tune down just because 'he is a man now'. In fact, he almost completely reverts to his regular girly self during the second half of the manga -aka, the second series of OVAs- when he's a ghost (for example, when he teases Miaka about how she and Taka "finally did it".)
Also, I am 100% open to hear other people's opinions on this because it's been years since I deserted FY-fandom and I've probably missed tons of discussions and essays on the matter.