1. Once someone has replied to your message you can't delete the conversation. If you could perhaps implement a "request delete" or something, so that if everyone agrees you can delete a conversation tree? Right now my "feed" is cluttered with lots of test convos. Another solution might be having a separate .json file for every user?
2. It wasn't obvious to me how you shared files. The "Set hotkey" option in the preferences should maybe be renamed to "Set file share hotkey" or something, at least explain a bit better without having to go the FAQ.
Other than that, looks good for a beta! I got a really strong "why didn't I think of that" feeling when I first tried it :)