I was surfing on the web and trying to find a chat app that uses Bitcoin address instead of phone numbers or any other identifier. Do you know about any project in this field?
The idea was around for some time, and as Pieter mentioned, using addresses without any additional obfuscating seems like a bad implementation.
There are few other projects, the one that is most serious is Microsoft's ION decentralized identity project. It's not the chat-app itself, rather the way of signing into apps using bitcoin-generated identity.
When it comes to chat apps, there is a pretty rapid development in the field of lightning network. As messages on LN are onion-routed, it seem to be a good idea for privacy-preserving communication. There are two projects I heard about, self-custodial Juggernaut and centralized (so what's the point) Sphinx.
I'd be very hesitant in using these solutions, they are working as untested, beta-version projects, so they may not be as stable and secure.