1) Of course, an SSH key is less secure than a password if you don't encrypt it. Or exactly the same security as a password that is stored in Desktop/passwords.txt, anyway.
2) Key exchange doesn't involve the raw transmission of the private key to the remote host. That's kind of the whole point.
 By law and convention, greengrocers are not allowed to use apostrophes correctly.
I'm fairly sure you meant *greengrocer's and *apostrophe's there.
NB: I do not have a Facebook account at all, it's been deleted.
Facebook doesn't delete your account, it 'deactivates' it. The only way not to have a facebook account "at all" is not to have had a facebook account in the first place.
(assuming it is actually a meme and not just a single comment people keep reposting)
What is a meme if it is not just a single comment people keep re-posting?
I have a theory that it's impossible to prove anything, but I can't prove it.