I'm of two minds. On one hand there's the good old "Whatever's fun at your table" standby. On the other hand, as someone who likes playing with newcomers, this kind of thing can really, really distort expectations of how tabletop gaming works and end up either discouraging people from trying it or encouraging them in ways that set them up for disappointment. Having to explain that you do not have a 5% chance of momentarily achieving omnipotence can really kill momentum. It'd probably be perfectly all right if people were clear they were playing with house rules but that preface is never given and consequently it's misunderstood as how the game's played by default.

you also shouldn't have a 5% chance to cut your own arm off