And those two facts are related. Quora actively drives casual users away with the forced-login behavior. So the only people on Quora are the people with strong incentives to do so... that is, people who are being paid. Marketeers.
Generally, I find Quora to be a pretty "ok" place to have a conversation. Better than most of Reddit, for sure. (Reddit does have some fantabulous subs to be sure, but not very many! :-) )
EDIT: HN is good for conversations in threads, although they can veer off track pretty wildly. Reddit can get pretty vitriolic. You could have a conversation, but the participants destroy it. Twitter? Fuggedaboutit. Are there sites I ought to look at where I can have a polite discussion with people that I may or may not agree with on various topics? [FWIW - Before 2008, Reddit itself was pretty close to this, except for maybe /r/politics]
OTOH a lot of legitimate questions were answered by specialists or people very familiar with the subjects