You get a little rant and a free tip for a bonus post today. In my humble opinion there is just no reason to ever thump a mic to see if it's working or un-muted. Most mics are pretty well built these days so it's not like you're going to kill it. Well, unless you've got a ribbon mic on stage but... well yeah, there's a better way people.
If I'm standing on stage with an MC mic in my hand and I want to make sure it's on, I just hold it up to my mouth and very softly make a "tst" sound or two. My brain knows what my mouth is doing and can check with my ears to see if they heard it reproduced in the room. 999 people out of a crowd of 1000 won't notice that I did it. I can even do it when there's someone else speaking and not disturb them.
Moving on to the line check. With the exception of a handful of mics that are designed for super high levels like kick drum mics, there's no need to walk around the stage tapping things to make sure all your patches are good. Just walk up to the mic and scratch the grill. With a partner at the mix the channels can even be muted and they can just crank the gain to see if your scratches light the meters.
And that by Brethren of the Knob and Fader, is your sound guy lesson in stage etiquette for the day.