> A single night of 4 hours sleep, followed by a year of normal nights sleep will lead to a me that is indistinguishable from the me that slept 8 hours that same night. [...] I'm all for sleeping properly, but lets not suggest that it is the end of the world any time someone doesn't get their standard n hours

I think of it kind of like burning yourself on a flame. Yes, a second degree burn will heal, and in a year you won't notice it, but if you do it over and over, or really burn yourself, you'll scar or kill nerves and never fully recover.

You do actual damage to your brain when you don't sleep enough, and it will effect your memory and cognition permanently if you do it too much.