I was a very active Quora user on 2010-2011, I'd visit the site over 10 times a day, I would write any answers on Word, make sure they were thorough, well written, etc, before I replied to question. I made an effort, both offline and online. What I really enjoyed was the initial community, the well thought questions and answers. During this 18-24 month period I also got thousands of upvotes, lots of thank you messages for my answers, etc.
One day an army of moderators came along. These moderators weren't Quora staff, but volunteers. I get it, it takes considerable man power to go through many of those questions and answers. I can work with that.
It was when I asking a question on movies & documentaries that I had my first encounter with them. I can't recall the exact question I asked, but it something along the lines "what are the most interesting documentaries released in 2011?". One moderator, without contacting me, changed the question to something more specific, he added a sub-genre to the question. I got notified of the change, went back, and changed it to the original question. After a couple of hours I get a message from the moderator telling me that that question isn't a "good/relevant" question (I'm paraphrasing). I ask why, and I get told that "You can't ask generic questions". Once more, I change the question to the original one and ignoring the random argument by the moderator. Then this moderator contacted a second moderator in order to gang-up on me, supporting each other random policies in order to make a statement.
It was then that I realised that these people didn't like to moderate Quora for the content quality, but for the feeling of 'power' and control moderation creates. I noticed that these guys liked being moderators because they enjoyed telling others what to do, with no regards for the content, quality, or users. That same day I deleted all of my questions, answers, and Quora account. I haven't used it again since then, and it feels great.