There is quite a lot of older P.A. system gear in operation all over the country (and world.) Most of it had a capacitor/resistor combination tying one side of the A.C. line to the chassis for noise suppression.
Bear in mind that most such gear did not
have a polarized plug, indeed most came with instructions to the effect of "in the event of excessive hum/noise, reverse the AC plug..."
It would not take much leakage or breakdown of that cap/resis combo to cause a strong or fatal shock. Even if the combo was on the neutral side of the line, there would still be potential for enough leakage to cause this.
A lot of houses of worship now seem to go with wireless microphones for baptisimal pools and other portions of services where there is contact with parishioners.
Normally the microphone would be grounded.
Depends. Older gear, "grounded" to chassis, yeah. But not in the proper sense of the word grounded.
Some modern gear uses isolated, electronically balanced inputs. So the shield of the cable (and body of the mike) may or may not be grounded. Take some voltage measurements from mike to a known ground on your next gig and you may be surprised.
I've been bit a few times by "hot mikes."