Every bug is the result of an imaginary computer that doesn't work exactly like my computer does and triggers a bug in my code. The code works on my machine, so this imaginary computer never existed and will never exist.

Signed vs unsigned chars, and the accompanying extension rules, have already bitten me switching between x86/ARM compilers. Confused the hell out of me when I was just starting out with C.

If you're going to interpret C as in "C on amd64, running on Linux 7.0 on an Arrow Lake Intel processor" then yes, you can get away with a lot of UB. That mitigates the problem but doesn't make it go away.