I think I’ve been overtightening QRs

I was taught that it should leave a mark on your hand to tighten a QR and actually kinda hurt your palm. I’ve been doing it like this for decades.

I’m starting to have my doubts though. First my wife pointed out to me that it is simply not possible for her to remove her wheel when I’ve tightened her QR… Secondly, I’ve noticed that with the type of QR in the picture that has the plastic cam guide, I always end up deforming that plastic. The pictured one is brand new, I just put it on and have opened and closed it a few times

I’m kind of confused now though how tight should a QR be? You don’t want it so tight that it could be undone by someone catching a foot or some clothing on it right? Not sure where the correct middle ground is.