When I first read your thread I wondered why you were putting tape on your mic head and whether it was some sort of performance trick that I didn't know about.
I can't tell you for sure whether it's true or not, but tapping on the microphone head could damage the thin, delicate diaphragm inside the mic. If it's tapped firmly, especially more than once, it can also create an audio spike which could cause damage as well. In all of my years of teaching children music and helping with the church programs I've seen many a kid and adult do that very thing and no microphones have been ruined. Of course, I tell them not to tap on it, but it seems like an ingrained habit that tapping is how you test the mic. It's not a good way to test the microphone whether it causes damage or not.