As for me, the moss doesnt affects the health of an orchid. They have symbiotic relationship with each other. They share signs of good conditions of climate. In the first place when you look at the moss which is green, it means the health condition of your plant is fine. But if they are too much moss in its surroundings it means you don't need to water much because the moss growth indicates the presence of water. Sometimes the moss dies out because of too much watering.
For me, I just leave the moss growth as it protect the roots from harsh sunlight or hot dry air and also a nice ground cover for the plant.