I would be curious to know exactly what the "black" mold is and what it's properties are.
Molds are so awfully many. It generates when moist respiration air rises to the upper feeder, moisture condensates and makes dilution on surfaces above syrup line.
Sometimes mold denerates white cloud in syrup and that I pour away. Sugar is so sheap that I am going to play with that. "I am not sick or poor".
But as Michal said, bees stand mold. However I try to avoid it. Bees carry naturally water from contaminated waters, from manure sludges and so on, but it is good not to mention to honey customers.
I have seen that bees are quite sensitive to fermented food during winter and whole hive may die if food is not good. Bees just come out from hive.