if I'm using a friends rifle, I don't mess with his settings
That is a very good point. I do not mind if someone changes mine to suit their vision but I never change the settings on a scope belonging to someone else.
Funny thing about that. I shoot with an LEO a lot and I sometimes get to shoot his service rifle. His eyes are quite different than mine and when I look through his scope, I really have a poor picture. The reticle is WAY out. Consequently, I can never shoot his rifle as well as he does. Because of his line of work, I would never change his eyepiece. Yet when he shoots my 700P, he always says the picture is fine and he is able to shoot about as well as I do with it. Might be the age difference in that his eyes can better accommodate the difference in the sight picture. I don't know.