When did Peak truly feel regret and shame for having "tagged" the buildings? -From peak the novel

boccaccio employs the voice of his narrator dioneo to represent his ideas on the tension between masculinity and femininity.  while dioneo excites the members of the brigata and recognizes women for their unique skills and independent ideas, he concludes the decameron with a story reminiscent of the society from which these young aristocrats escaped, revealing misogynistic overtones.  dioneo boccaccio is able to explore the gender disparity which is inherent in 14th century florentine society.

it was a big part of the story, making a lot of plot points happen?

i think the first one, it makes the most sense.