As a potter and art teacher, I thought I would add my 2 cents to the discussion. Mold is excellent for clay, and the more the better. When I was in art school, we would regularly mix up large batches of clay to use. When mixing porcelain, we would want to speed up the aging of the clay. Aging makes the clay more plastic, as a few in this discussion have already pointed out. One way to age clay slop faster before drying it out for use is to add things like coffee grounds (the more acidic the better) and other food waste. Yes, it smells a bit but when the clay is ready for use it is generally aged and very plastic.
Mold adds to the aging. It is also wet mold so nothing will be inhaled. I have never tried anything to take away the mold nor the smell. My students accept it as part of the aged clay.
I add vinegar to the slip that we use for joining clay pieces together. I don't really have a recipe for it; I fill a container with clay slop and blend it well to make it smooth, then add some vinegar. This helps in the binding.
I don't think there is need for concern over the mold in clay, honestly.
Halifax, Nova Scotia