You only get a low visibility notice ( https://signal.org/blog/images/safety-numbers-advisory.png https://signal.org/blog/images/safety-numbers-advisory.png ) w

You only get a low visibility notice ( https://signal.org/blog/images/safety-numbers-advisory.png https://signal.org/blog/images/safety-numbers-advisory.png ) which the counterparty can immediately scroll off. And even there, if I send a message to you and on receipt the software finds that your key has changed, my client sends it again to the new key. Which means that even if I was savvy enough to catch the message, it's tool late and potentially a critical secret has already been disclosed to a MITM by the time I see it.