The last post just about kills the EC idea. But lets throw in a couple more points just for fun
: EDM removes material from the surface of comets and creates water from the material somehow.
EDM involves sparking between electrodes. Sparks are quite visible. No such sparks have been seen in the images that have been taken of comet nuclei. The best example are the details images of Tempel 1. Thus the EC idea requires EDM sparks that are invisible in X-rays and visible light.