When I was growing up, my exposure to the deaf world was limited...school and whomever was around (rare occurance). So, I lived in the hearing world and I got to observe many things firsthand. The problem was I didn't always understand, but I learned quickly to go with the flow. Always knew I'd figure it out later on.
One of the things I learned without questioning was the habit of waiting for the person to invite you inside when you visit. We all know the drill - you stop by and you "announce" your arrival by knocking or ringing the doorbell or showing your face. The person greets you and decides to let you in or not. Simple, right?
Not so for an average deaf person who grew up in the deaf world. Why? They know that others will see them "talking" and they don't want eavesdroppers. The hearing people only have to worry about talking too loudly and the deaf people can be "heard" from any considerable distance. I've signed to people from 5th floor, clearly without any need to shout. LOL
So, to hide from the eavesdroppers, they just walk in and start talking. I started living with other deaf people at a college dorm and it was a huge adjustment for me to make when they would just barge in after I opened the door to find out who was there.
Some time later in that year, someone brought out a horror flick about vampires. It was "Fright Night" and I grinned when I made the connection between the hearing people and the vampires - you don't enter a residence unless you are invited in. Therefore, you are all vampires. ;)