In The Adventures of Tom Sawyer, you aren't going to hear Tom and Huck discussing the finer points of the subjunctive, or even talking about the earthshaking power of literature. No, much of the power of their language comes from the way it's written by Twain. He works hard to capture the rhythm of each character's voice and put it down on the page. Language is, for Twain, a huge part of a person's identity. Bad language – bad as in poorly written, over the top, etc. – is a travesty. When it's good, though, it can be very powerful.
For Twain, how something is said can be just as, if not more significant, than what is said.
In The Adventures of Tom Sawyer, a character's speech, the way he or she talks, is closely tied to his or her identity.