I don't think there are any issues that would prohibit ginsanko from being mirror polished. The reason why ginsanko is not mirror polised I recon is because the ginsanko being a stainless-ish steel primarily is made for the professional kitchen and line work in rather harsh environments. For professional use a mirror polish will make the knife perform worse than one with the grind marks, as food sticks a lot easier to a mirror polished surface than a rough one. So I can think of no reason to mirror polish a ginsanko knife except for the looks. Mirror polishing a carbon blade, however, will make the blade more stain resistant, but still you will have the issue with food sticking to the mirror surface.