As Kahneman explains in "Thinking Fast and Slow", System 2 (the reflective system, the one we want to be working a little on HN) is lazy and prefers to rely on System 1 (the reflexive one that deals in subsecond responses). I think the protests of HN readers when a title isn't trivially digestible or doesn't quite match expectations are largely the grumbling of System 2 that it needs to get up and move around a bit. And that's actually good for us—not the grumbling, but the working a bit. So the expectation to have titles spell everything out is a mildly bad thing and it's salutary to thwart it a little now and then.