I created a test container at /(root) level /test and am unable to edit /test/.acl with the sharing pane : error 404.
It goes with issue #94 . When you stop specific sharing for /public you delete /public/.acl and you never can edit it anymore (error 404).
I suppose that it needs to change /.acl to make it a usable default or to create /test/.acl on error 404 in sharing pane