If an electronically modified version of your signature is treated as a unique instance of your signature, then what's to stop someone else from copying your signature, making a few modifications, and using that as a unique instance of your signature on a different document? Is there some way of modifying your signature that would only be available to you, and not to anyone else with a raw copy of your signature?

And wouldn't anyone with a paper copy of your signature be able to scan that in and use it as a unique instance of your signature?