How we cite our quotes: Chapter.Paragraph or Chapter.Section.Paragraph (depends on whether or not the chapter had sections - some did not)
Quote #16
"Harry," said Lupin hurriedly, "don't you see? All this time we've thought Sirius betrayed your parents, and Peter tracked him down – but it was the other way around, don't you see? Peter betrayed your mother and father – Sirius tracked Peter down." (19.69)
Ow, our brains. Lupin places emphasis on Peter's name here, which is significant. By stressing Peter, Lupin sort of drags him into the spotlight, trying to force the others to see Peter for the traitor he is with the power of logic and rhetorical strategy. Rhetorical strategy is a fancy-pants way of saying that Lupin is speaking carefully here. He emphasizes Peter's name with a specific intent, not just for the heck of it.
Quote #17
"You fool," said Lupin softly. "Is a schoolboy grudge worth putting an innocent man back inside Azkaban?" (19.7)
Snape is sort of the poster child for grudges. He refuses to let go of his own past and, as a result, things go rather spectacularly awry for him. Lupin's word choice really belittles Snape too. Lupin references Snape's "schoolboy grudge," which implies that Snape's feelings about Sirius are childish.