Wonky rules question regarding AC.

[B.T.]

Thicken skin says that "[y]our skin or natural armor thickens and spreads across your body, providing a +1 enhancement bonus to your Armor Class."

The text for enhancement bonuses says:

An enhancement bonus represents an increase in the sturdiness and/or effectiveness of armor or natural armor, or the effectiveness of a weapon, or a general bonus to an ability score. Multiple enhancement bonuses on the same object (in the case of armor and weapons), creature (in the case of natural armor), or ability score do not stack. Only the highest enhancement bonus applies. Since enhancement bonuses to armor or natural armor effectively increase the armor or natural armor's bonus to AC, they don't apply against touch attacks.

Thicken skin provides a +1 enhancement bonus to AC; it does not provide an enhancement bonus to armor, a shield, or natural armor.  It's just a bonus to your AC.  So, my question is, does it stack with armor that has an enhancement bonus?  (For instance, if I cast thicken skin and am wearing +1 plate mail, do I have +9 AC or +10?)

[PhaedrusXY]

Most people interpret it to add an enhancement bonus to natural armor, and assume the way it was written was a mistake. Otherwise, it is very weird and doesn't really play well with the rest of the AC-boosting effects in the D&D rules.

[war_thog]

Yeah. It looks like a poorly written way to say +1 Enchancement bonus to natural armour. Go with RAI and follow the flavour. That's at my table anyway. RAW rarely gets a look in.
Fix it and move on

[Kerrick]

It's the same as barkskin - that one adds an enhancement bonus to NA. This is what common sense would dictate, and common sense overrides the RAW. Besides, you can't simply enhance "AC" - it has to be a specific facet of AC - natural armor, armor, shield, or whatever. It's really poorly written.