Have you noticed that the use of dalmatics is becoming more and more popular in the US? I had never even seen one in person until about 2 years ago. They are beautiful outer vestments that can be worn on almost any occasion, except penitential periods like Advent and Lent, since they are traditionally considered a “festive” garment. And it’s not even just the deacons who are making them more popular. If a priest is functioning as deacon/subdeacon, he wears the dalmatic. Even members of the episcopate have been spotted with them. But this is definitely appropriate, since as Fr. Z. explains so well, a priest (or bishop) is still a also deacon.