Humor, repetition of events and theme, and suspense are literary devises used in ch. 23.
Students often miss the humor inherent in the novel because it is subtle. However, the humor is evident with the opening line of chapter 23: "I wish Bob Ewell wouldn't chew tobacco." Atticus utters this after Mr. Ewell spit in his face.
Another humorous moment occurs later in the chapter the topic of in-breeding is broached, when Atticus talks about the Cunninghams.
Repition is used throughout the chapter too. Jem brings up the point again about Atticus being a great shot. This can help build suspense. Will Atticus have to use violence to protect his family? What would have to happen to push him to that?
The reader is also reminded of the stand Atticus took against the old Serum bunch that came to lynch Tom, but Atticus faced them with just a newspaper in hand.
Suspense is building for Tom too, for on page 219 we learn that Atticus feels that Tom has a good chance to go free or get a new trial. Yet, there is also the threat that if those don't happen, he will be put to death.
The theme of standing in someone else's shoes and looking at the world from their perspective is evident when Atticus explains to the kids why Ewell is so angry at him. This is a key reminder to the children.
The chapter ends with a reminder too of Boo Radley who fascinated the kids early in the novel but has faded from the scene with the trail.
umm dialogue and comparison are major language techniques in this chapter