Correct, the entire goal of defining it in terms of the C ABI is that C is the lingua franca that every language already speaks, so anything built on top of tha

Correct, the entire goal of defining it in terms of the C ABI is that C is the lingua franca that every language already speaks, so anything built on top of that has a dramatically lowered barrier to entry. I assume that the grandparent poster was thinking about making it possible for hypothetical future languages to someday be able to forego supporting the C ABI entirely, which is certainly a laudable goal (there's plenty of historical baggage there), but what the Rust developers care more about here is simply being able to do FFI that's safer than what currently exists.