These two struck me as the most interesting.
1) We discount our own prosocial acts because we know that we do not always have altruistic feelings. Stout emphasizes, though, that the prosocial acts are what benefit society. I would say that in a well-ordered society, the laws and many of the acts that benefit me are in line with conscience. All three motivations - following the law, seeing how helping others helps me, and following conscience - are normally all mixed together in our feelings and motivations.
2) The banality of goodness: it is so common that we do not notice it. In particular, we do not notice the many acts of passive altruism - the ethical restraint of not doing bad things even when it might be in our material interests to do so.