My wife and I both took our CCW classes from the same instructor, at different times. He was carrying an automatic in a paddle holster, with no magazine in it. Every time he pulled the gun to show something, he racked the slide to show that the chamber was empty. I thought it was a bit over-the-top at the time, but having read about so many training "incidents" I changed my mind.
I keep my Ruger on me most of the time; not that I'm worried someone is going to break into the house, but it's less hassle to leave it in the holster than to remove and replace it as I go outdoors and return. My wife only carries hers on occasion, and her gun is usually put away in a different room. So when she's shopping for yet more CCW purses or bags online, she'll occasionally ask for my gun to measure from.
I pull it out, drop the magazine, lock the slide back, and hand her the gun and the magazine. She drops the slide, does whatever she does, then locks it back and hands the gun and magazine back to me when she's finished.
I don't carry a round in the chamber, for reasons that aren't relevant here, so I don't have to contend with the "catch the loose round" and "bullet setback from repeated chambering" issues.
I don't view it so much as a safety issue as "starting from a known state." There's absolutely no question about whether the gun is loaded or ready to fire.
My wife agreed, particularly since her gun is identical to mine, just a few digits off on the serial number, and hers is always ready to fire. It would be easy enough to get the two mixed up...