@SMickey,
Well no, it's more like what was said in the first clip.
He says. "Look at this, it's an article (a magazine article) written by an organ, in the first person.
A lung can't talk, a complete lack of surprise can't talk, smirking revenge can't talk.
He is anthropomorphizing these things. Giving human characteristics to objects, emotions, etc.
He is being ironically funny when he says these things.
What makes it funny to the audience is that the people he may be saying these things to, like the supervior, has no idea what he's talking about. We are in on the joke because we saw and heard him talking about the articles.
You'd really have to watch the whole movie or read the book to get the whole impact.
For instance, in the "I am Jacks smirking revenge" scene. This guy hates his boss. He would love to get revenge on the boss, get him in trouble. When the boss calls him into his office to fire him. The guy sees his chance. He says "I am Jacks smirking revenge, and punches himself in the face. Then he throws himself around the room, making himself a bloody mess. Of course, people are going to assume the boss beat him up behind closed doors, because no one would be crazy enough to beat themselves up, right? But this guy is crazy, or going crazy. So....he gets his smirking revenge.
In the movie, that characters name is not Jack. We never know what his name is through the whole movie.
If I were to walk up to someone and say "I am Jack's broken heart" they would have no idea what I was talking about.
But, let's say a friend knew I had recently broken up with a boyfriend, and was sad. If this friend and I had found these magazine articles called "I am Jacks spleen, I am Jacks left testicle" and later on I said to her "I am Jacks broken heart". She would know what I meant.
So no, it's not done for lack of a better explanation. "Jack" depending on the rest of the statement, is his lack of sleep, smirking revenge, etc.
In a different book, a character would occassionally fall into a state of depression, and during that time would to harmful things to others. He referred to those times as "the bad gunkies" I guess because these bad thoughts were gunking up his mind.
So, if he hurt someone, he could say "The bad gunkies did that"