Absolutely agree 100%.
One other terrible thing about mental illness like that (as if there needed to be another) is that it's really, really hard for people with mental illness to navigate the healthcare system to get proper treatment. Even I've experienced this, with ADHD. I joke that I take medication to remember to take my medication, and that's sometimes kinda true. I can only imagine what it would be like with delusions of persecution and voices in my head telling me to do stuff.
Another thing is that in the US, it's incredibly hard to get someone like Terry on medication if they don't want to be, even if it's in their own best interests. Most of the time, I'm generally in favor of this stance, as I don't think that anyone else, particularly the government, should be able to force medicate people against their wills. (NB: I'm not talking about vaccines here.)
The unfortunate result of these things is that people with really severe mental issues can easily end up homeless, or, at the very least, on disability and unable to work, and there's nothing anybody else can do about it.
Schizophrenia in particular is a real bastard of a disease, as you noted. Apparently, symptoms only go away in 70% of people who get treatment, and 15% of people with schizophrenia end up institutionalized.[0] The symptoms apparently also trend less severe over time, but there can be sudden and severe regressions.
Terry got dealt a bad hand, it's true. But, I don't think it's fair to say that getting banned from a website led to his death. If that was all it took, then just about anything could have caused him to go over the edge.
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[0]: https://www.webmd.com/schizophrenia/schizophrenia-outlook#1