I read the white paper; I publish in computer science, which method are your referring to, more specifically?
I also see the team read Stafford Beer's viable systems stuff; very good!
I like the interface; will there be support for typesetting mathematics? MathJax like Wordpress and MathOverflow, or something like Overleaf?
Privates keys are encrypted using Triplesec a triple-paranoid, symmetric encryption library.
Mathematics typesetting will be integrated in the editor for online courses using something like KaTex.
Who guarantees the security of private keys when stored off the Steem blockchain? That's likes saying, trust me with the keys to your bitcoin wallet.
Centralised storage is asking for trust in these services that they will not be abused. This cannot be guaranteed, by the service provider. It also makes it a target for hacking.
No, your keys are stored on your computer just like Steemit, we never touch your keys once, but most importantly you don't have to put your password again and again, since the encryption algorithm enable you to just put a PIN code with an even better security as comparing to Steemit.
It does not offer better security than Steemit, because the app still has to login in through Steemit security. You've only added an extra step.
Yes it does, your private does not pass to steem nor steemit nor any other platforms. it stays on viper which stay on your computer. When you post something, your private keys also does not leave viper, they are just used to sign that it comes from your account. Check out Steem for more information.