Interoperability as currently called-for …

1. extends the social graph beyond individual platforms so that they crosslink with each other, leak disjoint identities, etc; see: XKeyScore
2. sows confusion regarding any particular platform’s security (“…am I using E2E in this group chat, or not?”)
3. any new, secure platform that gets big will be hobbled eventually, to the eventual benefit of state security and intelligence services
4. provides natural opportunities for cleartext interception at “bridges”
5. provides natural opportunities for downgrade attacks; e.g.: bridge Telegram users into iMessage chats, copies of everything end up going to Telegram
6. provides natural opportunities for user error (“…oops, I sent that over SMS / Telegram Cleartext / …”)
7. disrupts ongoing e2ee development (“…they can all switch to Matrix” / “…they can just implement MLS, which is still a draft standard…”)