As sympathetic as I am to Four, the Dauntless worldbuilding, especially, drives me up the wall. I suspect I'm supposed, like Four here and Tris in an earlier book, to feel surprised or shocked at the habit of Dauntless elderly and sick to off themselves, but all I can think is "How has this not been obvious to you all for years?" Hell, I picked up on it long before they did and I don't even live in this stupid world. If you spend years interacting with a group of people - because there is interaction between the factions, in school and so forth - and they skew young in the same way that Dauntless does, surely that should raise some questions in the mind of anyone with a) two brain cells to rub together and b) the tiniest modicum of curiosity.

Also, going to bother people while they're studying is the perfect example of why I have no sympathy for this particular faction. I find them obnoxious.