Ability to add comments to folders would be very useful. These comments should also be visible (permanently or optionally) in the shared (public) view.
Imagine I have a library of medical papers on a specific disorder, with folders like Pathophysiology, Genetics, Epidemiology, etc. These names, although precise, are not intuitively understandable to a lay person, and being able to add an explanation would be very helpful.
Note that box.com supports folder comments, also in shared view.
Regretfully, paperpile does not sync folder structure to Google Drive - else, the folder comments could mirror/sync with Google Drive folder comments.