You know, there are in fact studies about how people tend to vote/rate things and it is already proven that people tend to rate/vote more negative when they are having a bad day.
This is completely different than wondering if they are "generally unhappy people," which is a much broader and more significant claim than the above.

But as I pointed out almost immediately, this is really just tossing out an unempirical vibe check, and it's based on curated content, not a random sample of anything. So there's not much reason to think the impression itself is even accurate (or, even if it is, to what degree). It's a very reductive and simplistic explanation for things that have much more elegant explanations. I pointed out all of this and got little response, as I recall.

I don't know if you're not really interested in the discussion part of this, or if there's just no discussion to be hade (because, again, it's just messy off-the-cuff speculation), but either way I don't see the point in this continuing.