It came up on the Discourse channel last Thursday (@Shadow_Night_Black and @Hobusu, I think?). The reasoning was that armour goes into a common pool, so temporary armour effects work by implicitly adding a later effect that removes the same amount of armour as they originally added – they can’t remove the armour they specifically added, because they can’t find it. Similarly, in the case where you cast Art of War before attacking, you don’t choose which point of armour is pinged.
1 Like