Inkscape often does a number of unrelated changes when saving an SVG, not sure if these are just formatting changes in the source SVG text or if there's more to it. Either way this makes adding new icons hard since you want to avoid these unrelated changes. Saving the file in a new Inkscape version every once in a while should mitigate the problem a bit. Regenerating the icons (e.g. through `make icons`) shows no difference in the output. Note that I also ran "Clean Up Document" in Inkscape, but that doesn't seem to have changed anything/much.