The way the story is told is the clue here: Boccaccio writes this as if Pamfilo, the first of his storytellers during those ten nights, is having a great time recounting his outrageous story. In those days, everything narrated in this tale is horrific, especially the corruption of a final confession to a priest. Pamfilo made this character sound entertainingly immoral, corrupt and evil. This is the first tale, which is meant to shock the listeners and prepare them for a series of scandalous stories. And it does: ‘Pamfilos story elicited the mirth of some of the ladies and the hearty commendation of all, who listened to it with close attention until the end.’ (Boccaccio 1348) [My italics.] They really enjoyed wicked tales.
The listeners laughed because the way the tale was told suggested that Ciappelletto had a great time deceiving clients, traders and all those he came in contact with: he had a corrupt but wonderful life, full of the wealth he made from devious deeds. This vindicated him in the eyes and ears of the listeners, who were there only to enjoy themselves listening to shameful tales. In those days, it was even sinful to listen to a shameful story, and poking fun at the Church was considered risquè and entertaining. It was great fun, so the more wicked Ciappelletto sounded, the more he was redeemed, according to the