> although I think he discounts the usefulness of being able to diagnose system state at failure points.
Yes, this is the part that I do not understand. "Debuggers are terrible as a design tool, so... better not use any for investigation?!" That sounds a bit extreme.
Linus prefers not to see any kid playing with sharp knives in the kitchen, since they are only supposed to bake cakes. He is concerned about any blood accidentally polluting the kernel: fair enough. But that does not explain why he, an adult, is also not using any.
Wait: maybe he is secretly using a kernel debugger. Just like any other parent: "do what I say" (not what I do).