I think this thread is raising interesting questions about the currently heated discussion in ROK about gender neutral restrooms. The author is legally male, but identifies as a woman and visually presents herself as a female.
She is saying that male users of male restroom react to her with surprise when she enters a male restroom as herself. So she has to hide inside one of those doors not to be engaged with anyone with curious gaze towards her genitals (to see whether she has a penis).
She prefers to use female restroom because she can use it without being disturbed by other users' curious gaze towards her. I guess she's basically saying that she can blend in much better in female restrooms because of her appearance.
The reason why this discussion is so heated in ROK is because many cisgender heterosexual women are reacting to those transgenders demanding their rights to use gender neutral restrooms with fear. They are afraid of potential crimes in those restrooms because they are traumatized by the homicide crime happened inside a gender neutral restroom in 2016 near Gangnam station. (Traditionally there have been many gender neutral restrooms in ROK not because we are so transgender friendly, but because Koreans love financial & spatial efficiency. But many women got terrified after this incident and demanded separated restrooms in more areas.)
So I think the most important question we have to ask here is, why do they think female-only restrooms are safer? Usually there is no way to tell if a restroom user is legally male or female. Also there is no way to tell if someone who looks female guarantees crime-free environment. Many participants of this discussion are just handling this issue as if it's some kind of conceptual work. But if you really think about the reality of the situations.... you will understand there's no way to perfectly estimate the probability of crimes only based on sex.
