> I said, 'by default'. I know that it is possible to do a manual verification, but I am yet to have a chat with a person who would do that.
I'm not sure what else you'd expect. The alternative would be for Signal not to handle key exchange at all, and only to permit communication after the user manually provides a security key that was obtained out-of-band. That would be an absolutely disastrous user experience.
> Also, the Signal does not give any warnings or indication that chat partner identify is manually verified
That's not true. When you verify a contact, it adds a checkmark next to their name with the word "verified" underneath it. If you use the QR code to verify, this happens automatically. Otherwise, if you've verified it manually (visual inspection) you can manually mark the contact as verified and it adds the checkmark.
