This is really ignoring how relevant and affine types interact with different features. For example, unwinding makes perfect sense with affine, not so with relevant. Rust has unwinding, and no effect system to track whether something can or can't unwind.

I also make it very clear that the implementation is mostly free. It's just using tools we already have with minor tweaks. Most of my issues are exactly the pragmatic matters: your standard library isn't built to handle it, nothing in the ecosystem is built to handle it, and it everyone has to opt into support for backwards compatibility reasons.