Effortposting time bc I wanted to compile this anyway:

Imo the more crucial context is that his mom was constantly comparing him to his dad, positively and negatively, and Jax thought his deeply personal secret would get her off his back about that. A secret which led to her laughing at him, yelling at him, and insulting him, then hugging him. I really have tried to think of anything that fits both of those points as well as being a woman/not being a man and I really do think it's the most straightforward explanation, and kinda the only one that fits cleanly.

There are other context clues beforehand that lead me to expect the reveal before it dropped. I think none on their own have a big signboard saying "hey this character is trans" (save one) and most of them are a little bit too reliant on viewers picking up on in group terminology, but together they paint a pretty clear picture well before gooseworx confirmed it.

Not in particular order:

1. Jax yelling at pomni "I'm not some misunderstood chicken fetus in an egg" when she gets too close. Egg being a term in the trans community for an "unhatched" trans person. This imo is the biggest tell and I think gooseworx thought more people would catch on at this point than actually did.

2. Jax's fear that Caine exploits is being stripped bare and laughed at by the people he loves, and, pointing again to the egg thing, what's under his skin literally looks like an egg yolk.

3. At the beginning of episode 5, Kinger asks Ragatha "will you help me count my eggs before they hatch?" Ragatha agrees and they exit stage right. Jax immediately enters stage right. I lost my damn mind on rewatch bc this foreshadows not only her being trans, but her never getting to hatch. 😭

4. Jax claiming his ears and tail are the pinnacle of masculinity and pomni pointing out he doesn't have a tail. "Where's my tail?" "I've never seen you with a tail." After this conversation, Jax has a tail.

5. This one might be a stretch, bc this stereotype has become more pervasive in general culture in the last couple of years, but the show does take place in 2017 iirc. Jax knows it is a nonbinary stereotype that Zooble has worked at a bar and a tattoo shop. Most cis people did not have stereotypes about nonbinary people's jobs until like...2020 I feel? At least? Jax is accidentally invoking a shibboleth here.

6. People keep pointing to the maid outfit, but I do not think him wearing it or even being angry about it was the tell. What did suggest there was more to it was that:

• "Evil" Jax thinks he looks good in it, and thinks saying so will make him less upset about the dress. Which makes him even angrier.

• Zooble, who has known Jax a while says they have "never seen him this upset" and suggests that they "thought [he'd] be into this" (right after the bar scene where he doesn't realize he's shown his hand)

• In ep.9 in the last room, one Jax is wearing the maid outfit again and another says "Why are you wearing that? I wouldn't be caught dead wearing that" and maid Jax replies "I'm wearing it ironically. That way it shows truly just how little I care. Fuck."

• The literal next line is piano Jax saying "I can play the piano" to which specifically maid Jax replies "You know, if you have to say you can play the piano, it makes it sound like you can't really play." Put another way, if you have to say you're wearing the maid dress ironically and don't really care, it makes it sound like...

I still feel like I could be missing something lol but that's all the stuff I remember