It is all about keeping the OS sane to give the users and applications a chance to be sane, rather than causing madness from the get-go. However, if the system

It is all about keeping the OS sane to give the users and applications a chance to be sane, rather than causing madness from the get-go. However, if the system permits arbitrary applications to be executed (which plan9 does), then it cannot be shielded from madness. Proof: plan9 has a POSIX compatibility layer (APE), a vt100 terminal emulator and a vim port. It even has an aging full-on linux emulator. I think it could run a really old version of Firefox, but the memory is vague. People swear by Mothra these days anyway.