If you're at max level and craft a superior weapon, you can NOT further improve its damage by using a whetstone. Tested it on a normal, looted weapon and it works. Tested it on a crafted level 4 weapon again and it works as well.
Also, why does "improving plate armor" requires CRAFTING and not BLACKSMITHGING? Makes no sense and it should be switched.
Any level above level 5 in Blacksmithing also doesn't yield any benefit (same for crafting I assume). So please cap it at level 5 (even if you add items), because it's very confusing. I thought I get even better stats when I have black smith beyond 5 until I tested it in detail. Wasted 4 skill points. =/