This is something I am curious about. Does anyone have experience?
I recently was in Phnom Penh, nice Delta miles for the PVG-PNH one way MU flight. Then I had to go to the US for business, so bought PNH-PVG-LAX-PVG-PNH on MU... nice price, PNH-PVG was a B class, so extra miles and MQM's.... but when I returned, I had no more reason to go to Cambodia, so skipped the flight.
I can't imagine an issue for this one time, but if I did something like this 4-5 times, would MU or any other Chinese airline catch on or every care? Delta probably would, eventually.