In Captain America: Civil War, there were multiple instances when Black Panther (T'Challa) was called Your Highness by the Avengers:
- By Lt. Col. James Rhodes, when Captain America, Falcon and Winter Soldier get caught by the police.
- By Captain America, During the fight between the Avengers at the airport.
Why is that? I referred to the Marvel Wiki about Black Panther but didn't get any info.