We all indeed have our own norms, and can only report on how we understand them. OTOH, our norms about upvotes and thanks didn’t come from nowhere. They came from other online fora we’ve already been using (Facebook certainly), and our societal norms of reciprocity and tokens of belonging to a community.
Yes, OP, I want to put a framework up for why we do what we do. I tend to do that.
Quora posits that questions aren’t the asker’s, but the community’s, and makes sure that the interface suppresses any sense that the question belongs to the asker. Including hiding the question’s author, and letting anyone edit it.
But that’s not human nature. Human nature still treats an answer as a transaction between a questioner and an asker. People still reference OPs and A2A’ers—much as I’m doing with you, Mary.
(I still think that “fuck is racist” commenter was trolling you, btw.)
And if you accept that transactional nature of a question on Quora, then you accept that the answer is doing a service, not just to Quoradom (and to the bots that Quora Inc is training), but to the asker. And the asker needs the service, since, as Yishan Wong’s answer to Why are my questions not answered on Quora? puts it,
Quora is a great place to write answers and to read answers, but it is not a good place to get your own questions answered.
So, if you’ve done the asker a service, a gesture of acknowledgement from the asker is reasonable to expect. I know that, whenever I see an answer of mine with zero upvotes, my first reaction is “… it wasn’t that bad an answer”; my second reaction is “… I guess my upvoter posse doesn’t frequent that topic.”
And my third reaction is: “Screw you, OP.” Because they, of all people, should be acknowledging that I answered them.
(And when they comment instead of upvoting, I then think “Screw you, n00b OP.”)
I treat the Thank You button as a rarer emphatic, like Michael Masiello does. I only became aware of it when I started getting it from the impeccably polite Edward Conway. I use it rarely—less when an answer is amazing (that tends to get a public comment), than when an answer represents a unique contribution, that noone else would likely have given. The fact it’s private rather than public becomes part of its meaning.
But then, like a good structuralist, I accept that meaning is all about the paradigm. Quora put that Thank You button in there, I guess I have to find a distinctive meaning for it somehow.