What is the difference between the first three feathers and the fourth one added by Ethne?

The first three feathers given Harry by his brother-officers were a token of prejudice and misunderstanding. When thinking of them, Harry winced but only from pain; pain of being wronged and misunderstood. The fourth feather, however, was added by his fiancée and meant much more than the three others. In fact, this last feather gave Harry an epiphany which made him reconsider his position, and exchange his initial state of silent reproach with one of active redemption that made him regain his lost reputation and respect.