User blog comment:C.Syde65/Introducing the New Site-Wide System for Non-Site-Wide Features/@comment-26408254-20170813070859/@comment-25239866-20170813220006

I'm fond of enabling this but if a js is used to add an item in a place where it cannot be added site-wide it will normally be rejected if placed on common/wikia.js but will accept in gadget perfix.