But people are looking at C3, Odin & Zig because they've determined that C is the wrong language for them; many have determined that it's too sharp. C3 has "safe" in its title, they're expecting fewer sharp edges.

I'm not asking for useful optimizations like constraints to go away, I'm asking for them to be properly communicated as being sharp. If you use "unsafe" incorrectly in your rust code, you invite UB. But because of the keyword they chose, it's hardly surprising.