C++ is so complex that you can take 10 C++ devs, put them in the same room, and none of them will be able to read any others' code because they've each written it in a mutually exclusive C++ feature set.
Have you written C++? There are no "mutually exclusive" feature sets. The only deprecated language features I can think of are auto pointers and trigraphs, and I have never seen them in the wild.
It doesn't really work as a joke if there's no truth to it.
I understand what mutually exclusive means. There are no two people writing C++ with no overlapping language features. I struggle to understand what you might even mean.
Non-equal subsets of the full language feature set? Yes, that will happen with any nontrivial language.
