Quora-like system is just matter of UI, feel free to create such :-)
For now, take a look at ChainBB.

As for privacy, it's not what Steem is designed for at least in his current shape. There was some basic implementation of private messaging (messages encrypted with memo keys), but that's not really a good use case for a blockchain based storage. Something that you would like to keep private shouldn't end up written permanently on the blockchain. Once your private key would be compromised, anytime in the future, all your past privacy is gone.