Hello. I am having the same issue.
Here is the scenario :
I have a group called "Family". This group includes user "Girlfriend", "Brother", "Sister", "Parents", "Step-Parents".
I want to share pictures with the group so I share it with read only rights to the group "Familly".
I also want the user "Girlfriend" to be able to edit (delete pictures she doesn't like) and add some pictures to the shared folder. To give her edit rights I had to create another share with only the user "Girlfriend".
What the user "Girlfriend" will get is a duplicate folder.
Here is an example of what we get :
The folders with a (2) are a duplicate of the folders above. The storage space is counted twice (in this example the "Shared folder" is 8.3GB big instead of around 4.2GB big.