This is the question that hurt my players' brains:
Does the enhancement bonus from a suit of armor stack with Mage Armor? For example, X is wearing leather armor +2, and casts Mage Armor on herself. Does her AC go up at all?
Nope.
The DMG states that an enhancement bonus to armor is a bonus to the armor's armor bonus, not a bonus straight to the character's Armor Class. So wearing a suit of leather armor +2 gives your AC a +4 armor bonus, rather than a +2 armor bonus and a +2 enhancement bonus. So neither the leather's "mundane" armor bonus nor its magical enhancement bonus stack with Magic Armor.
Does the enhancement bonus from a suit of armor stack with Mage Armor? For example, X is wearing leather armor +2, and casts Mage Armor on herself. Does her AC go up at all?
Nope.
The DMG states that an enhancement bonus to armor is a bonus to the armor's armor bonus, not a bonus straight to the character's Armor Class. So wearing a suit of leather armor +2 gives your AC a +4 armor bonus, rather than a +2 armor bonus and a +2 enhancement bonus. So neither the leather's "mundane" armor bonus nor its magical enhancement bonus stack with Magic Armor.