@busy.org developed an open-source solution for any third party who wants to build an app on Steem, its name is SteemConnect. It does the authentication process of the users and give access to the public profile information.
Comments are disappearing when you haven't gave Busy (through SteemConnect) the necessary permissions (e.g. for posting).
Oh I see. Just so you know, I was not prompted for credentials (maybe was asked for an account name some time ago, but definitely not within the last 1 to 2 weeks). It would be nice to have a check to provide them when submitting the comment (or article) rather than loosing the work of entering the text. It's a test case to note for future revisions of busy.