> Something that makes Zig harder to learn up front, but easier in the long run is lack of undefined behavior.
Reminds me of the old discussions of Fortran Vs C, and specifically in the early times before C had a standard library. What we call "undefined behaviour" was just an idiom of the language where the "behaviour" was sometimes on purpose, but recognised might not be portable. And so the point here is the idea of undefined behaviour is tied to portability on some levels, and isn't just some purely academic idea about the compiler or abstract syntax trees.
So I'm concerned about the potential over-zealous prejudice against undefined behaviour, but I think we can all agree deterministic software is better than otherwise. The catch is that sometimes UB is deterministic, and yet dares to not be idiomatic.