> To be pedantic, Go strings are immutable and will carry different pointers to different underlying rune slices,

I wasn't thinking specifically about Go for this example, but alas Go's strings aren't trivial objects, and so this data race would be immediate UB in Go, whereupon "Susan Sarcemin" while still very unlikely is not impossible. The text (underlying rune slices? really? I guess that would be on brand but it's a bad idea) isn't getting mutated, but your string typed value is, and that is a non-trivial object.