Thanks for your detailed response. I'm sure others will find it useful too.
>>>>First of all, you are essentially sending your private key to a remote web server (directory.io).
Not if I'm doing the public-private key generation locally on an air-gapped, unconnected computer - one of the reasons for my posts above. I would like to get hold of that code for personal use, but the creator has hidden it, unlike other websites that randomly generate public-private key pairs. I actually think that I could create the code if I really put my mind to it, something I might consider if I can't get that code.
>>>>Secondly, you still need to load that private key into a wallet software in order to spend from it.
Not if I'm keeping it purely for storage and not transacting with it.
>>>>Thirdly, because the private key is in an unencrypted form, if the private key is stolen, then the thief can spend your coins immediately. With wallet encryption, if your coins are stolen, you still have time to move them as strong encryption and a strong password will protect your private keys.
How would a thief steal it if it's committed to memory and the public key has only ever been used once - to deposit the money? You're assuming I'm using it for transacting. That wallet is cold and the private key has never touched the Internet.
>>>>Lastly, you would be reusing the exact same address over and over again which will lead to significant privacy loss.
Not if I simply put the bitcoin there for long term storage.
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The more I think about it, the better my idea becomes - for storage purposes, that is. Perhaps not for transacting.