My app is different because the auth is handled between peers. So it could only every be people you shared your ID with. Security is important for me on this project. Its more important than the app being popular. https://www.reddit.com/r/CyberSecurityAdvice/comments/1ev5kqn/is_this_a_secure_messaging_app/

People should not connect to strangers on this app because of the potential risks of IP exposure... But between people you trust or between your own devices, it should work as expected for testing.

As for allowing links with expiration, you basically have that already with what looks like the login/logout functionality. There is no actual registration, it's just a UI for creating and deleting crypto random ID profiles.

Lemmy and the fediverse is a good idea. The federation makes it so I can see Lemmy posts on mastodon. Etc... id like to draw a parallel in my app with the chat-view and the inteagram-view