I also think it's inaccurate to say there's A sanity waterline as opposed to different waterlines in different contexts.
You could always do a veil of ignorance style thought experiment and ask how crazy you would expect things to be for you if you were a person chosen at random at a given time and place to try to sum over some of the contexts.
Should differences in agency be accounted for somehow? If there's a single god-emperor somehow able to order absolutely everyone around in minute detail, should you consider only the sanity of the god-emperor, or also of everyone else, when all they can do is obey the god-emperor? The lives of the populace are going to suck, but will b...
If it's worth saying, but not worth its own post, even in Discussion, it goes here.