Survival Multiplayer:
I tried to repair a >50% damaged, enchanted diamond sword (Fire Aspect I and Bane of Arthropods II) with a normal >60% damaged unenchanted diamond sword with the use of the Anvil.

1. I put both weapons into their respective slots. The cost for the repair was 17, which was my current level.
2. I pulled the repaired weapon out of the slot and - APPARENTLY (not sure!)
3. I hit the inventory key (that's TAB for me) to exit the interface a second later.

But instead of the repaired sword plopping out onto the ground it was the two still damaged weapons. Additionally my level was reduced to 1. Of course I was pissed, so I tried to level up faster by using Bottles o' Enchanting. A single bottle raised my level up to 18. That must have given me back the levels I thought I lost. There were still there?

STILL when I put the swords back into the anvil to try again, the cost was raised to 28! And I hadn't used them, so they were still as damaged as before.