I don’t understand why UNA should use these outdated script. Mutation Events, including DOMSubtreeModified, DOMNodeInserted, DOMNodeRemoved, DOMNodeRemovedFromDocument, DOMNodeInsertedIntoDocument, and DOMCharacterDataModified, are detrimental to page performance and significantly increase the complexity of adding new features to the Web. These APIs were deprecated from the specification (iconSpec: UI Events) in 2011 and were replaced by the much better-behaved Mutation Observer API in 2012. The usage of the obsolete Mutation Events must now be migrated to the Mutation Observer.