That group of kids everybody knew in high school that individually were often the targets of derision and/or physical violence, but who through some geek radar found one another to form an alliance, thereby lessening the probability that any one member is a victim.
The reference to the middle-age practice of isolating individuals with Hansen's Disease (Leprosy) and not allowing them to come into contact with any "normal" people is apropos because if a "normal" (read non-geekified) child were to associate with the leper colony, s/he is immediately labeled as suspect, and in extreme cases will be isolated him/her self, thus becoming a member of the colony.
Mark's sister: "Mark has been indoctrinated into the Leper Colony and is at the park LARPing."
churchhurt is where you experience a degree of distance, pain, or judgement from your church community. Essentially, you are just unable to “find your place”. This is prevalent in the Christian community, but can be extended to other religions.
Now that I am an adult I am beginning to heal from the churchhurt that was inflicted on me as a child.
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.