In the spirit of Learning Stuff From Other People (part of my New Year's Resolution) I point you toward Joyce Carol Oates--someone I'm sure you know.
Recently I finished reading Zombie, a short novel by Oates, that covers the mind of Quentin P___--a serial killer in the spirit of Jeffrey Dahmer. Here's a small quote to get you in the spirit of things:
"Dr. E___ asks What is the nature of your fantasies, Quentin? & I am blank & silent blushing like in school when I could not answer a teacher's question nor even (everybody staring at me) comprehend it."
Here is the lesson to take from that: Punctuation is an art form.
Throughout the book, Oates creatively uses punctuation to get us into this killer's head. Here is a man who has no regard for human life, why should he have regard for human grammar? The punctuation of this novel is comprehensible and rebellious at the same time--just like her main character.
What does this mean for us as writers?
1. It means that we need to know the rules first. Yes, that means we do need to know what 'fragments' and 'dangling participles' are, and we need to know where to put a comma--or not. If we don't understand the rules, then we have no command over what we are actually saying. We think we're saying A but we're really saying B and it confuses the reader. As Lincoln said: "Those who write clearly have readers, those who write obscurely have commentators." I'm not gonna go into the rules here, there are plenty of books on the subject. Yes, they're dry. Yes, they may put you to sleep. But yes, we must read them and understand.
2. Use puntucation to add to the story. Once we know the rules, we can break them to make a point, to emphasize elements of the story itself. (Sorta the way poetry works). In Zombie Oates uses the & symbol to replace every single 'and'. To me, this signifies a character who is 1. lazy, because he doesn't even spell out a three-letter word and 2. doesn't give a crap, because he uses it throughout, flaunting language and rules--which he does in his character actions as well (killing people is definitely against the rules).
Challenge: Go over something you've written and see if changing a comma here or there doesn't mix it up. Throw in some parentheses. Use periods to make more fragments. Take out periods to make longer stretches of words. See what happens to the voice/tone of the story when you do that.