You right. It's slow and unoptimized for it. There is a clear reason this isn't a popular approach.
In the messaging app, I started off by making it so it worked with local-only data. It works over webrtc. I added bells and whistles like the signal protocol and multimedia messaging, but it lacks the ability to send messages offline (because webrtc).
The git approach can allow to publish encrypted messages for peers so when they come and online and your aren't there, it can decrypt a payload specific to them.
With git, it's hardly instant messaging, but I'm working on a feature where git can act as a peer-broker to establish a webrtc connection.
The git approach also would mean that it could work over tor with the signal protocol encryption (albeit hardly instant messaging).
It's a fairly unique approach and there are countless details to consider like how group-messaging would work. So I'll confirm it isn't ready to replace signal or any other app/service.
"Vibecoded" doesn't quite have the bite these days. I've clearly used AI, so let's get that out of the way. In my open source projects I tried to provide code, documentation, live examples. You can find out more about the open source projects at: https://positive-intentions.com/
Feel free to reach out for specifics. While this project is not open source (yet?), I am still trying to make some comprehensive docs.