I take your point about a safety issue, yes of course you shouldn't stand by and watch someone poke grass down the static vent. We all know that it should be blown down firmly
Sorry, this was a joke (some very strange poeple read this)
My first example occured to me, I had landed a greaser and was cleaning up when the instructor grabbed my hand and gave me a 5 minute lecture on why it was DANGEROUS to take up flaps, put carb heat away etc. before we had come to a complete stop on the taxiway.
I started flying one month before this instructor was born, he told me that as he looked at my log book, just seems to me that as he wasn't teaching me basic flying skills, he should have let some things go.