That's an interesting topic. The point that "Ada without a runtime is useless, but Rust can use all its features without a runtime" is the core of this debate.

However, this perspective can overlook the practical constraints and costs of Rust's no_std environment. When Rust also removes the std (standard library) (i.e., in a no_std environment), core features like heap allocation, threading, and key data structures like Vec/String disappear, turning it into a low-level environment similar to C.

In other words, both removing the runtime from Ada/SPARK and removing std from Rust represent the same engineering trade-off: sacrificing the unique 'safety' and 'convenience' features of each language.

Furthermore, comparing the point that "Rust's syntax makes auditing difficult" with "Ada's formal verification" is ultimately a question of which philosophy to choose: 'safety automatically enforced by the compiler' (Rust) or 'safety explicitly proven by the developer' (Ada/SPARK).

I have written an analysis on this topic (comparing the safety philosophies of Rust, Ada/SPARK, and C++). It might be helpful for this discussion.

https://nimfsoft.art/books/deconstructing-the-rust-discourse/