I have been using Nabble forums for several years as a part of my MOOC-type courses at different universities. Thanks for being of great help. :)
That said, I recently discovered that some of my old forums have not deleted properly. They are still listed in my app list and display their old front page, The rest is gone though - clicking anywhere displays the "Site Not Found. Please contact Nabble Support if you need help. " message. But I would still like to get rid of them altogether (some of my forums have self-deleted, but not all of them).
I also had one of them that refused to delete, displaying a 500 error instead. I found a temporary solution (sort of) in reducing the access to just admin (me).
If you contact me, I will send you the app list that needs to be deleted.