and I'm interpreting the answer there as follows: "If you don't have applications that depend on atime's being valid, you don't need them."
Thinking about my home Linux system, which doesn't serve much of anything to anyone (and I don't use a local MUA, not that I'm aware of anyway), it seems to me like I can safely set
nodiratime). But maybe I'm wrong? Do some typically-installed apps use it still? I'm having doubts about this since I don't see why anyone would expect the OS to maintain atimes for everything just so that it can know the atime for a few files of its own.