Option for Clients to "star" or "favorite" Images

The option for Clients to "star" or "favorite" Images in a shared folder would be insanely useful. It's surprising this still hasn't been added yet as a feature. Especially given the introduction of Replay for video feedback, and the fact that commenting already exists for photos and stars exist for internal favorites—all we need is the option for external clients to also "star" photos the way they can comment on photos.

Currently, we have to use third-party programs to share photo proofs with clients just so they can select the images they want to purchase. Comments alone are too cumbersome when there's hundreds of images to go through. One tiny addition of a star would make Dropbox for photos unbeatable!