When I got to the part where the article dismisses memory protection, I just thought "wow someone never used any of the Windows 9x operating systems." Because in that space the lack of memory protection most certainly WAS user impacting, even single user...
The problem is that software is buggy, and without memory protections a buggy piece of code in one process can cause unpredictable things to happen in another. Essentially it turns a process which executes in a "knowable way" into one that executes in a arbitrary way.
Windows 9x suffered from this with drivers in particular, where a single buffer bug in one driver could cause other drivers to seemingly crash, and the root cause was incredibly difficult to track down.
TempleOS would appear to be a computer from "before the fall" - ie, before error crept in, in the form of viruses and badly-behaved programs... in the same way that the architecure of an IRL temple is designed to be a representation of heaven on earth.
I understand his perspective - computing in the 1980s was very much an age of innocence. The programmer's God/Genius is telling him to build a modern, developed version of the environment that he spent his healthy youth in. I don't suppose it's entirely beyond the realm of possibility that it might hold a key to resolving his problems and coming to terms with his illness.
It may be a trite comment, but in an environment where these conditions are treated as "holy madness" or shamanism, the sufferers have more of a place in society.
cf. John Nash, although Schizophrenia is a scale of greys.
It's funny you mention lack of memory protection in Win9x, because they did have memory protection. They just sadly didn't have it for one critical segment.
The problem is that software is buggy, and without memory protections a buggy piece of code in one process can cause unpredictable things to happen in another. Essentially it turns a process which executes in a "knowable way" into one that executes in a arbitrary way.
Windows 9x suffered from this with drivers in particular, where a single buffer bug in one driver could cause other drivers to seemingly crash, and the root cause was incredibly difficult to track down.