Fother Mucker on the island server was duplicating items using a known MCMMO duplication glitch. The glitch works on MCMMO's ore detection array.
When you place an ore, any ore, MCMMO records the placing of that ore so that when you harvest it you won't get double drops.
However when you place an ore, and then push it with a piston, MCMMO can't record the movement made by the piston, so that when you harvest it, MCMMO will duplicate the ore, because it considers it to be natural, and not player placed.
This is the duplication glitch she was using. She has been warned severely, her duplication machine has been destroyed, and 30k was taken from her account. If you catch her duplicating again, ban her, and post in the ban notices area.