There isn’t a way to pop them directly into Full-Screen Presentation Mode, Peter, but it’s something we have talked about enabling.
We have changed the way that Review and Comment works, however. When the editor is in Review and Comment mode (which it is when someone visits your project via the public link), users can click through the project as if it were in Full-Screen mode. So, while the editor isn’t in Full-Screen Presentation mode, it acts as if it were while allowing folks to view and leave comments as they click. We thought it was the best of both worlds.
Let me know if that feels like enough for you and your team, or if going into Full-Screen mode is a better solution. It’s something we are paying close attention to right now and would love your feedback.
Also, let me know if you continue to get a login prompt when visiting from the public link. That’s a bug we’d definitely like to get fixed.