I am generally a polite individual. I don’t swear (often) in front/around children. I only seem to flip off Denver drivers once or twice a day (usually on Colorado Blvd or at Hampden and Yosemite). And I hold open doors for people. I will walk slightly ahead of someone to hold open the door, usually after they jump back because they think I am being rude. I will also hold open a door for an extended period of time, to let a number of people in. I tend to like being the last person in a room.
It shouldn’t be rare for you to see it happen, be nice and do it for others.