While this is certainly possible, I would think you would have to almost do this on purpose. I cannot conceive of any method that I use personally to rack the slide that would result in the safety being engaged. Even in Injured dominant hand scenarios, the safety is engaged by pushing down on the lever. There is no reason why the backward motion of racking the slide would result in downward pressure on the safety unless you are trying to forcefully PUSH the slide forward instead of pulling back and releasing it.
...
The only way I could see it even pushing forward would be if you were pushing it from the back of the slide with your fingers directly over the safety.
...
If you spend that much time practicing tap and rack exercises and are still somehow flipping the safety on, what is the point of continuing the exercises?
I've seen a slide rack either engage a slide mounted (down for safe) safety accidentally or decock (down for decock) a decocker only gun. It can happen and it does happen. I've even done it myself a couple of times.
I can't figure out what you're talking about when you say that you'd have to push forward engage the safety. Pushing forward from the back would DIS-engage the safety. A backward motion (like a slide racking movement) would be what would tend to engage the safety, not pushing forward from the back.
Finally, it matters not what kind of manual safety a gun has, whether it moves up or down, around, in, out, over, forward, back, clockwise or counter-clockwise. Regardless of what kind it is, how it operates AND
whether or not you ever intentionally engage it, you should ALWAYS include disengaging the safety as part of the action of presenting the firearm to the target.
That's because when you present the firearm to the target you mean to fire the gun and one of the CRITICAL steps in firing the gun is making sure the safety is disengaged. Unless the safety is completely disabled, there is the potential for it to have been engaged and therefore your firing procedure should insure that it is disengaged.
Failure to do that could be irritating, embarrassing, or even deadly.
If your gun has a manual safety, you should be practicing to disengage that safety EACH and EVERY time you bring it up to fire at a target.
By the way, here are a couple of my babies...
