Thank you for the review. That's unfortunately impossible from a technical point of view to save a moz: page. I do not know what moz: page you want to save but if that's the reader view, note that there is a button in the annotation editor to format the page like in the reader view. If you have an account on github, I recommend to open an issue if you want to discuss about this.

Reply #2
THIS page cannot be saved with Firefox because Mozilla blocks extensions on some of their domains. You can use another browser like Chrome to circumvent this limitation though.