Build your perfect messaging app

We're in the golden era of security- and/or privacy-focused messaging apps right now. We have tons of choices including many which can be self-hosted. If you could pick and choose four features from existing messaging apps, what would you build? This is just for fun; don't worry about what features might be difficult to implement.

For myself, I'd take:

* Signal's encryption. It's widely regarded as the gold standard for secure messaging at the moment, but it has some flaws …

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