Kein Systemvergleich means “comparison between systems is forbidden.”  It is written here in the imperative, as an order. I don’t want to sound shrill, but I have to say this once in a while to the people in my environment.  Sometimes I have to say it to myself:  No comparing the university system of Country X with the system of Country Y, for instance.  Sure you can do it among yourselves, but not in front of people from Country Y (the loser in this example).