What difference does it make? ALICE When would you like to meet? BOB T

What difference does it make? ALICE When would you like to meet? BOB Tomorrow, 19:00, by the north tennis courts. ALICE Sounds good. !!! BOB's key has changed !!! BOB Actually, could we meet at my place? I'm going to be super busy tomorrow. If Alice and Bob are doing something that needs to remain secure, Alice would be a fool to trust Bob's messages after the key change without manually verifying the new key with Bob. How does withholding messages help, aside from telling the server which people have enabled the setting and which people have not? [edit: I just realized you were talking specifically about the case where manual verification is enforced for all users; disregard the last phrase.] Admittedly one angle I can kind of agree with is that layman users may not understand the implications of a key change and the importance of out-of-band verification, and blocking messages until verification would be a way of signaling the significance of the key change. But... counterpoint to that is that users interested in security are probably already dead in the water in that regard if all they have is a layman's knowledge of how crypto works.