During review stages and perhaps within the comment sections, clients should have the ability to access their own media library to link assets from their library directly into their comment.
There is no current simple way to do this.
Current process:
Opening an additional Shootsta Platform tab, go to media library, searching, locate the asset they want to use, download the asset, going back to their projects/comment, and re-uploading the asset... is far too many clicks and processes.