When an item's name is italicized it means that a player made the item. When they aren't it means that a staff member renamed it (i.e ET, GM, LT, etc).
That's not exactly what I was talking about, but I figured it out. When available for crafting in a crafting table, Nexus items have italicized names. When they are made and in the inventory, they have normal names. Still not sure why.