I feel like key revocation is usually solved via key replacement in most secure instant messengers. Every implementation that I know (which does not include Si

I feel like key revocation is usually solved via key replacement in most secure instant messengers. Every implementation that I know (which does not include SimpleX) offers some way to recover from complete key loss, at which point other parties receive a "the key for this contact has changed" notification, and that new key is then untrusted by default until verified out-of-band. (This does trust the server operators to not censor your re-registration, but that seems no different from most other centralized revocation mechanisms.) Do you have a scenario in mind where this would not be sufficient?