I'll point out again that C, the poster child for ancient language technology, has been able to evolve its syntax and feature set with attention to not breaking

I'll point out again that C, the poster child for ancient language technology, has been able to evolve its syntax and feature set with attention to not breaking legacy code. Excusing the lack of such attention via linguistic trickery about "defining compatibility precisely" does indeed kinda irk me. And disengaging doesn't win the argument.