Is it possible to set the rights of a folder and all its files in such a way that multiple defined users can add, modify and remove files within? I was hoping to be able to do that via ACLs and I got it working that multiple users can change files, but only the owner is able to delete those files.
Deletion modifies the directory, so the users need to have permission to modify the directory, not just the folders.
See these Superuser questions:
Linux - group member cannot delete file with rw permission
Why can't I delete a file where I have group write permissions on?