Great link, thanks. Unfortunately it led to a really intense reedit procrastination session. It did occur to me that there might be some kind of condition like this, and I thought about including that possibility but didn't want to qualify the argument and make it more complicated. I should have checked to see if there was such a thing. Anyway yes, qualify my previous claim with "with normal brain function".

The point I was making was more along the lines of 'don't assume you're clinically depressed just because you don't automatically notice meaning in things the instant you look for it', though.

Sure. My position is just that chronic nihilism is epiphenomenal to unhappiness except in cases of non-standard brain function.