But it is also wrong to reduce a language to what is in the spec.
Apparently reducing the language to what is in the spec is only a thing when talking about C and to some extent C++.
When other languages have compiler specific extensions beyond the spec, it is a failure in their design.
Yet when C and C++ devs have to reach out to compiler specific extensions, it is not a design failure like it is pointed out to others, rather an advantage.
It is also wrong to not apply the same measure when it doesn't suit the message.
This one of the failures of Linus T. with the linux kernel: he was not able to keep the assembly source code with plain and simple C code you can compile with a small and alternative C compiler (same failure for the glibc devs I think).
I don't blame him, he is already keeping the linux ABI stable, and pulling that off is something.
Any code that ventures anywhere near that territory is 99% Undefined Behavior. It's almost impossible to write proper C/C++ code that isn't UB while touching byte-level representations.