You will indeed fry a mod when splicing hot, and even if you don't most of your ac shorts end up self-healing (carbon's a pretty good insulator) so you'll never find it. I've done it just by plugging the sucker back in when the housing wasn't grounded. Anybody every ruined a car stereo by brushing it with the hot wire when it wasn't grounded?
I don't do it because I don't want to start a problem somewhere else. I don't want anybody else to do it because sometimes I'm on the other end of cable! It's happened, and when your firmly planted in a wet manhole 60V will scare you do death, and 90V will BURN. Don't make an orphan of somebody else's kids just so you can make your job easier. Wet skin has 1/50th the resistance of dry skin. How often are your hands really dry? Wicked scary? not really, but just wait.
