I had an instructor stalling the aircraft on final during my CPL training. Didn't much like it but it was a good learning experience. Things look a lot different down from 3,000'.
I have heard of an instructor who did this down to around 50 or 100ft in PA28s, used to demonstrate it as a way to lose height, can be done and has been done. What is the problem is inexperienced pilots with much less ability see this and copy it. The blokes who show off these manuevres have experience and some knowledge of when and when not to do it, they don't usually pass that part on after the demo. The students who witness the event then have a go and usually stuff it up. Instructors need to be leaders and keep things simple and to the point, even doing something and then saying "I'm experienced and can do that". leads a student to thinking maybe 10 hours I can do that on my 2nd solo etc... Do you specify how much experience is enough to bust a limit? Even on a simple navex diverting cautiously rather than pushing on may save the life of your student in the future, showing them how you pushed on and upgraded to IFR doesn't help.