It's a bit...odd in DoS at least. His defense isn't equal to his level anymore, but it starts higher (5). Armours now work inversely i.e. an armour with 6 absorb and a BB with a base of 10 would have 10-6 = 4 absorb, so really armours CAN be equipped, they just don't offer any benefit for the most part (thankfully you can use ribbons now without losing a heck of a lot of defense).

O, almost forgot, there's a bug whereby shops selling armour equippable will display that it will improve his defense (up arrow). Same goes when you use the "Optimal" command.