In the case which I am describing nobody other than you has your key.

But the key you are talking about the SSH client recognising is the server key right? Or did you mean after authorising your SSH client to connect to the unknown machine, and the key you were talking about was the identity public key? I ask because the thread you commented on was discussing users not looking carefully which servers they connect to when connecting to new servers, and that is based on the SSH servers key, not your identity key, which is why I said that if someone who is able to redirect your SSH connection to a different server also owns the correct servers SSH server key (as you said "just the ip/domain that changed"), then there isn't much the client can do to help keep you safe anyway.

> But the key you are talking about the SSH client recognising is the server key right?

Correct

> which is why I said that if someone who is able to redirect your SSH connection to a different server

I will try to be more clear. Often when I am away I use ssh to connect to my desktop pc which has a dynamic IP address. Even though I have already stored the public key of my server in known_hosts it keeps asking me to verify if I trust its public key every time that it changes IP address without even mentioning that it has met said public key before. So if I am not careful enough I might end up accepting the public key regardless, even if I am being MITMed.

Ah, yes, I've always found that to be a little strange. It is cryptographically possible for the server to establish to the client that it is who it says it is, just on a different IP

Sorry for the confusion, I misread your initial comment, thought you were saying it does what we're saying would be a good behaviour, and was confused as to why you thought this was a problem, but it was just I who was confused!