At my old college, we used to get messages from random faculty members telling us to make use of tutoring resources, or to not park in the street, that sort of thing. However, since we’re all encouraged to be as professional as possible, they had to be polite about it as well. I think what really made these emails come off as passive-aggressive was the punctuation. So many exclamation points, but the phrasing itself was very polite.
A more specific example would be when a professor asked as to refer to them as professor within emails and within the classroom. I don’t mind professors wanting to be called by their title, because they earned it. However, there’s something passive-aggressive about class-wide or campus-wide emails in response to a few isolated incidents. They also made it out into a behaviorist thing, where they were saving us from this awful habit.
Writing and Money 