With that said, they require verification of the signature on the back of the card with the one on the receipt / screen.
In the event that the card is not signed, you are then allowed to require identification and the card must be signed by the customer before it is used.
Most credit card companies prohibit the "See ID" that some people put on their cards in place a of a signature.
But writing "See ID" on the back of the card and then using a completely different signature on the receipt is not acceptable as far as I know.
It's all very silly anyway given that online credit card transactions almost never require a signature.
Quite honestly though, once a thief has access to your card, you have other problems. If they're close enough to see it, they're likely close enough to duplicate it and leave you the card with you ever knowing.
If the signature is that concerning, then use one signature consistently for your credit card transactions that's unlike the one you use for anything else.
If you don't like that option, then you probably shouldn't be using credit cards currently offered.
Now, this is all very hypothetical for many reasons, but generally it's my practice to follow cardmember agreements that I am, after all, agreeing to follow.