My 2c might not crush the scale, but FWIW I'd expect XMPP clients to be easier to work with if I had existing PGP keyrings that I wanted to re-use, favoring consistant identities and protocols over more stringent avoidance of key re-use. Could be a key on a smartcard, or the key your employer kept a revocation certificate for.

Conversations has great support for OpenKeychain on Android, and I'd love to see that come to competing protocol Deltachat but the devs are focusing on cross-platform behaviors atm. Android-specific fork Deltalabs might be willing to be upstream for it if anyone knows where to start with that.