> IMHO this "schism" was completely unnecessary and only happened because of ignorance and hubris

Having attempted to implement it correctly in slimcc, there are indeed some edge cases[1][2] that justify not adapting it fully.

[1] Unordered side effects; evaluation of expressions with overlapped destination is implementation defined but not listed as such (the wording in standard is "can potentially not be evaluated").

[2] Both GCC and Clang still get this wrong in 2026: https://github.com/llvm/llvm-project/issues/190858