Great question. Always one in the chamber. The sole exception being an old single action revolver without the newer safety bar where you carry 5 rounds instead of 6 so the hammer rests on the empty chamber. Even these guns were "designed" to be carried with all six, but it probably wasn't the best idea. Regardless, since this is a gun that must be cocked before firing anyway, it's not adding an extra step having an empty chamber because the cylinder will rotate to a loaded chamber anyway. Just some context.
Since you asked about semi-autos: It probably has not been addressed in your firearms courses because either they were not concealed carry/defense courses, or there was simply a presumption that you would be carrying with one in the chamber. The design and legal definition of a handgun is a firearm that, once loaded, can be fired with one hand. Nowadays, with there are even guns/rear sights designed with a high shelf so you can rack the slide on something if you are injured...after a reload or putting in a fresh magazine.
As for the safety: when you do training for defensive uses, there usually is a step in the process for taking the safety off. In the NRA courses (protection outside the home, defensive pistol, etc), this happens after you have the gun out of its holster and its pointed downrange, but before you pull the trigger. These step is for people who have safeties, but there isn't a step for racking the slide for those who carry on an empty chamber.
I personally only carry guns without them: Glocks, Rugers, Kel Tecs. Of those I have worked into the carry rotation to test them out, like the S&W Shield, I always ordered them without the thumb safety. For me, I like the guns to be like my Mac...just point and click.
During those infrequent instances where I would carry something that did have a safety, such as my Bersa Thunder (before it broke), the Walther PPK/S, or Beretta M9 I did carry them with the safety off because it seemed like an extra step. But then I had the realization that it could get switched on for some reason, malfuction, scuffle, whatever. So my thinking became, and I have no idea if pros follow this logic, "if it has a safety, use it. Just train around it." The 1911 brings up both your concerns where you have to use the safety if you're carrying one in the chamber ie "cocked and locked."
My experience from talking to others, either as instructor or otherwise, indicates that the reason most people carry an empty chambered gun is because they are just not ready. That's okay, just get ready. If you plan to train so much so that you can quickly and competently rack the slide, you're ready to carry one in the chamber anyway.
I carried an empty gun around for days in my house and out and about when I first got my license just to get used to the feel. But when I loaded it, I loaded it.
Lastly, don't take any of this too seriously. As long as you are comfortable carrying and shooting the gun safely (meaning you won't shoot anyone you don't intend to, including yourself), just keep practicing and do so.