Also I don't think the equivalence between edge/vertex versions is trivial at all (though maybe we just have different standards of triviality). For example, i

Also I don't think the equivalence between edge/vertex versions is trivial at all (though maybe we just have different standards of triviality). For example, in a grid like this: ..#### .....# #.#..# #...H# ###### A single wall placed (i.e. vertex removed) can block two edges, and it's not obvious what graph transformation can turn that into a single edge.