This logic resonates with some students. “Having these titles forces everyone to give that respect,” Lyndah Lovell, a graduating senior at the College of William & Mary in Williamsburg, Va., said. “They know they have to use these manners with everyone. Even if the underlying thoughts of prejudice will still be there to some extent, you give these thoughts less power.”

Insisting on traditional etiquette is also simply good pedagogy. It’s a teacher’s job to correct sloppy prose, whether in an essay or an email. And I suspect that most of the time, students who call faculty members by their first names and send slangy messages are not seeking a more casual rapport. They just don’t know they should do otherwise — no one has bothered to explain it to them. Explaining the rules of professional interaction is not an act of condescension; it’s the first step in treating students like adults.

That said, the teacher-student relationship depends on a special kind of inequality. “Once I refer to them as I would my best friend, I eliminate that boundary of clarity,” Ms. Lovell told me. She recalled how awkward she felt when the head of the research lab where she worked asked undergraduates to call him Willy. “All my friends were saying: ‘Oh, man, do we do this? He has a Ph.D. He’s a professor. Is it O.K. to do this?’ Sometimes I do, but he’s a great mentor, and it’s confusing. A lot of us like to preserve that distance.”

Alexis Delgado, a sophomore at the University of Rochester, is skeptical of professors who make a point of insisting on their title. “I always think it’s a power move,” she told me. “Just because someone gave you a piece of paper that says you’re smart doesn’t mean you can communicate those ideas to me. I reserve the right to judge if you’re a good professor.”

But she ruefully recalled one young professor who made the mistake of telling the class that he didn’t care if they used his first name. “He didn’t realize how far it would go, and we all thought, this is awkward,” she said. “I had no desire to be friends. I only wanted to ask questions.”

During office hours, we have frank conversations about career choices, mental health crises and family tribulations. But the last thing most students want from a mentor is the pretense of chumminess.

Ms. Lovell said the very act of communicating more formally helps her get some distance on a personal problem. “When I explain my difficulties and struggles, I try to explain in a mature way,” she said. “I want to know: How would someone older than me think through this?”