You are aware that D and rust and all the other languages this is being compared to don't even have an ISO standard, right?

Yeah, so their documentation serves as the authority on how you're supposed to write your code for it to be "correct D" or "correct Rust". The compiler implementors write their compilers against the documentation (and vice versa). That documentation is clear on these things.

In C, the ISO standard is the authority on how you're supposed to write your code for it to be "correct C". The compiler implementors write their compilers against the ISO standard. That standard is not clear on these things.

I don't think this is true. The target audience of the ISO standard is the implementers of compilers and other tools around the language. Even the people involved in creating it make that clear by publishing other material like the core guidelines, conference talks, books, online articles, etc., which are targeted to the users of the language.

Core guidelines, conference talks, books, online articles, etc. are not authoritative. If I really want to know if my C code is correct C, I consult the standard. If the standard and an online article disagrees, the article is wrong, definitionally.

Correction: if you want to know if your compiler is correct, you look at the ISO standard. But even as a compiler writer, the ISO standard is not exhaustive. For example the ISO standard doesn't define stuff like include directories, static or dynamic linking, etc.