When you put 2 pieces of the same type of diamond armour in a CraftingTable the result you get is 1 back.
You aren't giving enough detail... More than likely not a bug. When you put two of the same tool or armor in a Crafting Table, then "create" the item to the side, you are repairing. Minecraft's repair was added a couple versions ago. Durability from both pieces combine to make a higher durability piece of armor.
i think he means in the 1.1 update thats how u repair your broken items ... Ones about to break like this:
