For me, this chapter marks the point at which Gimli begins to "open up" as a character. We are entering the domain of his forefathers, the heart of his civilization, and the home of his cousin Balin, who we learn to our great distress at the end of the chapter has died with the rest of his colony. In this Moria chapter, Gimli takes a leadership role alongside Gandalf, exhibits his deep, glowing pride in the culture and accomplishments of his ancestors, and displays grief, nobility, and vulnerability at the tomb of Balin. In the next chapter, we get to witness his hardiness and courage as a warrior, his faithfulness to the Fellowship and the Ringbearer during a time of great danger, and his eagerness to share the beauty and magnificence and history of Kheled-zaram with Frodo and Sam. And then in Lothlorien, Gimli begins his journey towards rapproachment with the elves, his adoration of Galadriel, and the birth of his abiding friendship with Legolas.
Moria is a BIG turning point for Gimli.
“Therefore I say: Eä! Let these things Be! And I will send forth into the Void the Flame Imperishable, and it shall be at the heart of the World, and the World shall Be.”