My experience is the same. When I do get Quora, I do not have to sign up, and it’s usually valuable. I would add that the presence of a Quora result at the top of search-engine results usually indicates that my query is freaking arcane and specific, and Google is doing its best to show me _something_. In other words, it’s not as though Quora results are taking slots away from better results.
> usually indicates that my query is freaking arcane and specific
Exactly this. (That's what I meant with "Quora often shows up when the other results look unreliable or ad farms", but I didn't phrase that quite right.)
