Can make characters sound as if they are overreacting, screaming. There have been studies that show that readers scan newspaper stories for the quotes. Anecdotal information, logic and my own bad habits suggest the same is true for dialogue in fiction. So if there's something important to get across, you're safest having your character SAY it. As a sidelight here, those same studies show that scanners pick up most information from the beginning of a paragraph, next the end of the paragraph, and last the middle.
People repeat for emphasis and when they are under a strong emotion.
I will not have you running through the fields. The formality also adds emphasis. People talk in rhythms that are as individual as facial expressions. These rhythms tell a great deal about the person. Can indicate national origin, ethnicity, regional origin.