I don't think Henry tastes modesty in chapter 15. In Wilson’s letters, Henry sees weakness rather than an expression of humanity. When he realizes that he still has the letters to Wilson’s family handed to him before the battle, Henry does not think to spare his friend humiliation and give them back. Instead, he considers them a token of protection against his own shame. Yes, Henry ran, but he did so without witness (“in the dark”), so he can still proclaim to be a man. Wilson, on the other hand, made a show of his fear. Henry feels a budding superiority over the man who has not only fought valiantly in the battle, but who showed him so much kindness.