alt Hacker NewsCounterpoint: you could write a C++ compiler in a non-C/C++ language such that the compiler’s implementation language doesn’t even have the notion of C++20.
A compiler is perfectly capable of compiling programs which use features that its own source does not.
That's not a counterpoint—at least not to anything in the comment that you're (nominally) "responding" to.
So why has it been posted it as a reply, and why label it a counterpoint?