In that GT thread, several others posted their experiences, including one who racked the slide multiple times, but had a broken extractor, so without a visual / tactile chamber check, there was still a live round in the chamber... slide closes, trigger pull, BANG.
We can all use reminders to PRACTICE those safety rules that we all KNOW by heart...
We had a Soldier that had to learn the hard way about proper clearing procedures:
Outside of Army dining facilities, barracks, and admin. buildings there are clearing barrels set out to allow for the safe clearing of rifles and sidearms. At dining facilities, those barrels are usually monitored by a detailed Soldier in order to ensure compliance with the post policy.
We were involved in a training operation conducting perimeter defense of a field site, and we had our M-16s with blanks, MILES gear, and blank adapters.
So in a long line of Soldiers waiting for dinner, a Soldier took their turn at the clearing barrel, racked the charging handle, ejecting a live blank, and squeezed the trigger. BANG! Shocked faces all around. The Soldier looks puzzled, racks the charging handle again, and (predictably, to us) it goes BANG again... and yet a third time, BANG! Finally, some of the bystanders stopped laughing long enough to yell "Drop the magazine FIRST!"
The Soldier had to report to the Commander, and was assigned duty at the clearing barrel for each meal for the following week. I think that the lesson was sufficiently learned by everyone there...
On another note, I'll bet any of the service members who were overseas could tell some incredible stories... I know that EVERY clearing barrel that I saw overseas had at least one hole in its lid... that means not only was there a negligent discharge, but the barrel was not inserted into the mouth of the barrel either. I know, we always blamed those holes on the foreign security guards or on the contractors who were armed... it COULDN'T have been Soldiers or Marines, right?
Just remember, that the more we handle our firearms, the more comfortable we get with them... Sometimes, comfort breeds a casual or even a careless attitude... and with careless attitudes come careless practices...
As Mom used to say, "Let this be a lesson to you, young man!"