With bug 13417 a new permission was added to allow/disallow deletion of public lists. The lists permission doesn't work like other module level permissions as turning it off won't disallow use of the lists module. It would be nice if this could be added. It might need a 'remaining lists permissions' permission, so that you can only disallow the deletion of public lists but allow general use of the module.
I agree!
I'm documenting this now and find it very confusing to users. I'd love to see this fixed for 3.20. Nicole