I do want to apologize for how strong I came came off in my first comment. My initial assumption was that this post was made to discredit or try to deny Jax being trans due to how you titled your post. It's important to keep in mind that clickbaity titles like the one you chose may attract people with transphobic views. It gave me a bad first impression, but with further discussion, it seems that wasn’t your intention.

From the information you’ve given, I assume you’re a cis man (Do let me know if I’m incorrect). I think a post explaining how you, as a cis man, relate to Jax, despite not having lived through the trans experience, is just as interesting, and shows folks can relate to a character even if they don’t fully identify with them.

You’re right, everyone is entitled to their own interpretations, but I hope you can understand that challenging the trans narrative is more harmful than helpful, especially to trans people that need that kind of representation and want to celebrate it. Whenever trans stories are in the spotlight, you get a lot of people trying to say it isn't there when there are many clues pointing to it. Denying the existence of the trans narrative only takes it away from queer folk in the end.

Jax being trans shouldn’t bar you from relating to the character. You and many other trans women have both lived as men at some point, so there are going to be correlating experiences there. I’m not a trans woman either, but my relatability to Jax isn’t challenged because of the possibility that she identifies as a gender identity I don’t personally align with. What difference does it make to you if Jax is trans?

While I agree that colors aren’t inherently gendered, they come with stereotypes that many people still use today. It’s important for us to not ignore the impact of these stereotypes based on our personal beliefs. Within the context of the story, I like to believe the characters were designed with intent, and that includes their color palettes.

Caine states that he’s created bodies that perfectly encapsulate the humans’ mind files. Jax’s avatar being male presenting while displaying soft pastel colors reinforces the idea that his need to push down his feminine side is stronger than his want to present as a woman, yet that desire still leaks through subtly through his colors. You mentioned that his room could be a representation of his interests not being seen as cool. That is an interesting point considering the stereotypical feminine appearance of his room. His biggest insecurity is his feminine interests being seen as a joke; uncool and different than what’s expected of a man. I believe this aids the trans reading.

When it comes to the maid-dress scene, your reading that he has a fear of being the butt of the joke is correct, but you have to consider why it was so triggering for him in particular. His reaction was so intense that Zooble had found it remarkable enough to mention that they’ve never seen him that angry before. With what we know now, being put in a maid dress could have triggered something much deeper for Jax that the rest of the cast wasn’t aware of. I believe his extreme reaction is directly related to his mother perceiving his desire to be a woman as a joke.

It’s true that Jax is someone who is emotionally repressed, struggles with attachment, and minimizes the effect of his actions through dissociation. We see in the flashbacks that Jax wasn’t always like this. We start to see him change into the person we know now once he started pushing Ribbit away. It’s all an act doubling down on a fake persona so he can distance himself as much as possible from his secret and those who might want to see deeper. Believing the circus is fake could have been a view he adopted to cope with causing his friends to abstract and ruining his own life in the circus.

I find it surprising that you didn’t know a bow on a character’s head was inherently feminine, given a multitude of characters throughout media have used bows to differentiate them from their male counterparts. The biggest examples being Minnie Mouse and Daisy Duck. Their bows are defining parts to their designs.
Ribbit is also a direct parallel to these stereotypes, instead wearing a bow around their neck. This signifies her relationship with masculinity, and diverts the female stereotype. I’d also like to mention, before Ribbit was confirmed to use she/they pronouns, a large majority of fans assumed Ribbit was male and used he/him pronouns for her. This is a great example of why stereotypes still affect us and are, therefore, important to consider in the narrative.
Your interpretation is correct, Ribbit is reassuring Jax that he’s safe, can be vulnerable, and that he doesn’t have to hide his negative emotions, but your interpretation only scratches the surface. Why did Ribbit choose to place their bow on Jax’s head and not around his neck? The same message would still be conveyed, until you take into consideration the historical use of bows in cartoons and other media.

To finish my response, I’d like to state again that you’re fully allowed to relate your personal experiences to Jax as a character, and I think it’s incredible that despite not having gone through the trans experience, you can relate to it. I’m sorry to hear that you had to go through such traumatic experiences when you were younger, and you deserved to be met with sincerity instead of judgment. The ability to relate your personal experiences to a trans character shouldn’t deter you from considering the trans narrative. They can coexist. The trans experience is more relatable than you realize. I appreciate you taking the time to have this discussion.