There's no good way to manage trust between users because the services have to be interoperable. Look at messaging services like Telegram or Signal; end-to-end encryption is easy because they're single entities who decide how all messages are sent and received on their platforms.
I don't think communication services themselves have to be interpretable to manage trust correctly. See PGP used in email, git, package signing, etc. - completely unrelated actions, same trust network.
