Possibility to download the version from the web, and work locally with the desktop version.
But for the long run:
If I upload that file again, all comments etc. are lost. From my point of view, download could be sth like creating a new branch, which could be eventually merged to FramerWeb (which serves as a master?!), with all comments persisting.
Go to File > Download and it will do just that. (Note that you will need the Framer Beta to open files, and the desktop version might be a bit behind sometimes during the beta period.)