As I understand it, currently the term "schizophrenia" is used by the lay public incorrectly as 'generic-crazy' and by MH professionals to include a catch-all of similar-presenting but biologically different syndromes. I'd hope that by the 31st century they'd have nailed the term "schizophrenia" down to one specific definitive diagnosis and that's what Thom has...but that's probably giving DC too much credit.
And yeah, I think Thom's a positive presentation of someone living with a MH syndrome - he's generally happy, and his ethics are very much intact - he knows right from wrong and lawful from unlawful, and back when this JSA title started his doctors emphasized how deeply murder scenes upset and disturbed him. His faculties are also intact - he can do higher-level maths, and he'll often point out a wrinkle in a crisis situation nobody else noticed. So yeah, on the whole I don't feel too bad about laughing with him.