Hopefully this won't become a tool for the Flat Earthers. =)

Might be a tool against them. Note that Mt. Everest isn't on the list. If the Earth was flat, all the tallest peaks would be seeable from one another unless a specific peak taller than one of them was exactly in the way.

We're actually thinking of writing a SIGBOVIK paper where we explore running this whole thing for a Flat Earth!