Consistency is certainly important, and we agree that doing the most intuitive thing for non tech-saavy users is usually the right option.
However it is not just dynamic images that we need to think about. We also have users that specifically avoid having the images they use on Supernotes anywhere on the web, by using the path to the image on their hard-drive as the image URL.
However the real issue is that our current editor is not really equipped to handle such asynchronous behavior (uploading a pasted URL in the background), so any “auto-backup” solution would probably need to come alongside the new editor we are building, which will be able to support features like that.
We will of course keep iterating on ideas around this and post here as our thinking evolves! Thanks as always for helping us figure out the best way to add new functionality.