Elite Frequent fliers, except Gold, can select MCE seats at no additional charge at the time of booking. (I believe Gold can get a 50 percent reduction in the cost at booking time, and for free if less than 24 hours before flight). So, if there are MCE open at the time of the flight, that would generally mean there are no elites left that want them, and AA will assign them to other passengers who do not have seat assignment. What YOU paid for is the ability to get the seat in advance. What do you mean by "clearly should not be there"? In any case, I do not understand your complaint. You got what you paid for. If Elites aren't using them, the people without seat assignments have to sit somewhere, so AA will sit some of them in MCE. Do you think it would be better for AA if it just IDBs them, instead of using MCE?