> An extended grapheme cluster is largely defined on "this visually displays as a single unit", which isn't necessarily correct for things like "display size in a monospace font" or "thing that gets deleted when you hit backspace."
I'm sorry, but I fail to see how "This visually displays as a single unit" could ever differ from "Display size in a monospace font" or "Thing that gets deleted when you hit backspace".
I'm sorry, but I fail to see how "This visually displays as a single unit" could ever differ from "Display size in a monospace font" or "Thing that gets deleted when you hit backspace".