In a case like this, I don't really see how hiding the user level would help. Sure, you could give everyone the same icons and not display it there - but you can't hide their actual role in the organisation - because people need to know who other people actually are.
The list of professors within the organisation isn't really something that you can keep secret, and you can probably find out what most other people do either internally, or just by looking at their profiles on sites like LinkedIn. Even if you do hide the icons for staff, when someone's job title is "Head of IT", or "English Literature Professor" then you can have a pretty good guess about the type of user account they have.
So ultimately you're going to make making the system less user-friendly for no real security gain.