Hi Rahman,
Thanks for the report. Both problems are fixed in the working-1.6 branch.
A username can now be an email address. The user form accepts “@”, and mixed-case names from the identity provider save correctly. Delete no longer asks for a password. It asks you to confirm, and the button shows how many items will be deleted. The FOG_REAUTH_ON_DELETE setting is removed.To get both fixes, update to the latest working-1.6 and re-run the installer. You do not need a plugin update. Until you update, you can turn off FOG_REAUTH_ON_DELETE in FOG Configuration to stop the password prompt.