Please read again.  The folders are not contained in each other, they are two separate folders. 

For example:

/media/Folder 1/

/media/Folder 2/

/media/Folder 3/

These are all separate folders, they can not be shared, only the first one shared can.  Ubooquity seems to think Folder 2 and Folder 3 are sub folders of Folder 1.  This is a bug.  If I share Folder 1, I will be blocked from sharing Folder 2 and Folder 3.

I meant more like content rating, like mature, general, adults only.  This field is in the comincinfo file, it just needs a database field and supporting UI.

I'm noticing the same problem in 3.0.2. The spaces around any & in folder names are collapsed and Moonreader returns the same error.  But, it only seems to happen on Moonreader.  I tried it on Librera and it works correctly, so I'm assuming it's a bug in Moonreader.

I just realized folder sharing can be limited to users.  But individual content ratings as found in the comicinfo file would still be helpful.