Is there a way for specialists, security journalists, and the public to audit the app, the security protocols employed, and/or the code base? And are there people who can at least vouch for Torsten's technical qualifications and character?

I think that not having sufficient information about the technology itself or the person who is behind it will forever work against the effort to popularise the app. People have been burned time and again by improper security implementations and owners who turned out not to be who they said they were.