A child is restrained in bed for weeks at a time, in an attempt to exorcise a demon. The child actually is possessed, and the perpetrator seems to believe he's making progress, though we never see any indication that this "treatment" actually helped anything: it certainly did not expel the demon.
One strange creature, peeking out between its own fingers, will exclaim a digitized "YOU WHORE!" if John moves in its line of sight. In addition, a more hidden note mentions child prostitutes casually as anything.
Period-accurate to the 80s, too. An obscure note from someone who seems rather conservative refers to people with "GRID", or Gay-Related Immuno-Deficiency. This was a name given to a disease we now know as AIDS, and was retained by homophobes in an effort to keep the stigma on. The context of them being mentioned is the writer listing forms of people that he wouldn't mind getting eaten by a bizarre monster he found.
One note in the middle of a clearing starts as a news article, but slowly becomes more and more off until it's a diatribe against the reader and then a mess of Latin. It can even cause your controller to vibrate, which isn't done anywhere else in the game.
After a harrowing note that goes pear-shaped, John is stuck in the middle of a ritual with effigies in flames and seemingly melted into a horrible creature.
While the whole thing may or may not be real, the events seem to mess with John by insinuating that he's lost his sanity and is hurting people because of it.
A note in the graveyard is from the perspective of a woman who lost her infant partway through the pregnancy, with the implication of another woman being responsible for...satanic magic reasons.
Characters are described as using and being addicted to crack cocaine; mentions of 'ruined drug addict bodies' are made, and a character makes rather severe moral judgement on them. There's also a tunnel said to be the hideout of killers, tweakers, and other scum of society.
Michael has been kept from his parents for a very long time to the point that they are demanding to see him again via letter. Father Garcia has his reasons, but it's not fun for anyone.
Galore. Around every corner in the graveyard. Also brace when the camera gets shaky in the church, after seeing the text "I'M HERE, JOHN", and when seeing a nun-like entity.
One ending is bittersweet (your losses persist, John is confident he can keep on and do what's right). One ending is far more bitter (John doesn't trust himself, and a suspicious vehicle follows his own). And the last one, which you really have to try in order to get, is John turning tail and joining the Satanists.