Since 2017 an increasing number of lawyers and judges have used the parenthetical “(cleaned up)” to indicate that internal quotation marks, alterations, and citations have been omitted from a quotation. Recent editions of Introduction to Basic Legal Citation have recognized the practice. On February 25, 2021, it made its first appearance in a Supreme Court opinion, one written for the Court by Justice Thomas. None of the briefs filed in the case contained “cleaned up” quotations.
The (legal citation) landmark case is Brownback v. King. For more, see Debra Weiss, Justice Thomas goes rogue on the Bluebook with ‘cleaned up’ citation—to the delight of appellate lawyers, ABA Journal (March 15, 2021).