About lens coating:
Optician Harold Dennis Taylor observed that older lenses on the shelf passed more light than new ones of identical design. He investigated and discovered that the older lenses were “bloomed”. They had acquired a thin layer of schmutz thanks to the London smog caused by coal burning brought about by the industrial revolution. The “bloom” increased the light transmission by about 4%. Taylor patented a lens coating process in 1904.
By the end of World War II, most cameras sported coated lenses. The coating mitigates reflections off the polished glass surface. Today we coat in a vacuum chamber depositing layers of barium, cadmium, sodium, lithium and magnesium etc. It is the thickness of the coat that does the trick. The coat must be ¼ of the wavelength of the light ray to be controlled. A modern lens is multicoated, each coat to handle a different color. A modern lens with multiple elements, each coated, is greatly improved as to speed, plus the coating reduces flare and ghost images.
The coat on the front and rear surface is quite durable and likely not harmed by normal lens clearing. If the front lens coat is injured, likely you will never see any degradation.