You can't delete a folder. You can only remove it from the catalog and then delete it in Finder. To save time finding it in Finder, you can first do "Show in Finder" and then remove it.
You can delete a folder from the disk from within Lightroom if the folder is empty. In fact, it doesn't even ask you if you want to only remove it from Lightroom or delete from disk. This should be changed to the same behavior as photos so it will ask.
To delete the folder (if it is empty), rightclick the folder name and chose Remove. It may appear empty in Lightroom but there may be files in the folder as far as the OS is concerned.
Thanks for this. Will try your suggestion when time permits.