Digital QR codes make bitcoin vulnerable to theft. Transmuting digital Bitcoins into a paper medium means the QR code reveals your underlying location. Scanning that QR code means anyone can anonymously steal Bitcoins. Thats the bad part about anonymizing a currency. Masking ownership means no audit trail to recover a thiefs digital fingerprints.
What are you talking about? QR codes are for public addresses. If I'm going to send my bitcoins to you and we're together physically, then I can just scan your QR code instead of copying the text of your address. I don't see a private key that's in QR code. Maybe it's just me or that it doesn't really exist at all. And, if someone can really just steal your bitcoins, then that should have happened a lot of times. Most times people get hacked because their computer is infected with virus or that they accidentally gave their private key to someone. QR code is not in the situation.
You want no audit trail or any public ledger? Then go ahead and use black bytes from Byteball. They don't have any of that. It's completely anonymous.