This is super longwinded but I'm having trouble putting the ideas together concisely, apologies in advance to anyone reading.
I generally hear people describe being trans as feeling like you were born into the wrong body, like biologically male with a woman's soul in some sense. But my experience with being cisgendered is one of feeling like my spirit would belong wherever it was born to. I identify as a man and would feel out of place in a woman's body, but if I had been born into a woman's body I would feel out of place in a man's. That's my mental picture of what being cisgendered is. I'm not sure I'm articulating this great but hopefully it's coherent.
That gives me the impression that being transgendered is an emotional discomfort, and I've wanted to hear an opinion on if the resistance to labelling it as a mental illness is because of the societal stigma against mental illnesses and how some people think successful treatment should always mean suppression and never accommodation (which would look like gender-affirming care if being trans counted).
Part of where this is coming from is I've been dealing with my own mental demons lately after some traumatic experiences in the past couple years, and the way I think about it is different when I'm looking inward. If it's another person behaving strangely it is easy to say they are suffering and deserve care, but when it's me I am a crazy person doing crazy things and I know better.
I do feel inclined to see being trans as a mental illness (for the reasons I've given above). I believe I'll be open to hear what I'm getting wrong there. It's not something I've ever been comfortable enough to ask though because I expect that statement to be received offensively (for the reasons given above). I get a lot less hostility in general over who I am and I still sometimes have a very strong gut reaction to perceive that stuff as an attack.