I don’t know Ruby, but I’m the next best thing, a programmer 
I can see a few problems with this script. It seems to check the group names to see if someone’s an admin or super mod, but admins can rename those groups or create custom admin / super mod groups.
Do you have any custom admin or super mod groups?
If I recall, there’s a cancp column on the groups table which designates someone as an admin (I’ve wrangled the MyBB code / database before), which should be used instead.
If I learn Ruby, I should open a pull request to fix that. Moving on.
I’m going to check the phpBB one to see if and how it handles bans.