As pointed out to me last week by Bulia, I was incorrectly reading the path_t information produced by Potrace, and putting it into the d="" attribute of a <path> node.

Potrace's own SVG generator uses a duplicate curve on "internal" subpaths. One is used for the reverse-winding to produce a "hole" in the filled area, and another is used to provide opacity to that hole.

Since we are not using the information like that, and are only concerned with the curves, it is best to remove the redundant subpaths, which we are now doing (as of today). Now the traces go faster, look better, create fewer nodes, and are thus easier to edit and drag around.

Bob