I did not tell the players that I was tracking their sins. When they reached Runeforge, I used the surging sin-magic to create “flashbacks” to their characters less than benevolent actions. This served as a great device to remind the players how far they had come over the three years of our campaign, and it gave them fresh reminders of their character's habits, which made roleplaying the surging emotions easier.
This folded nicely into the effects caused by the Runeforged weapons, and the Prideful character in our group has become almost intolerable now that he has a Domineering Runeforged weapon. It has all made for great flavor as we wind up the final approach the Mhar Massif.