Can Enchantments Be Overridden?

[*Pellease]

Sweet!

[*Neutral Zone]

Items with three existing enchantments can be upgraded... Sometimes. It's a little buggy. Sometimes it works, sometimes it doesn't. Might depend on the exact enchantments or the item type. I've upgraded cloaks with all three slots taken before, but generally it's better to play it safe and make sure you always have a slot free while upgrading.

Certain enchantments are also ignored by the enchanting system.

I know the following properties are ignored:
Material Properties (NOT things like +1d8 damage provided by materials, but the "Material Type: Cold Iron" type stuff instead.)
Properties which provide only penalties (Such as on cursed items.)
Damage Reduction (Such as that provided by adamantine items.)

[*Alersia]

DR and materials are granted via another option, thus they stack.

Special Materials are different because they grant material slot + 1 enchantment.