Irony punctuation is any proposed form of notation used to denote irony or sarcasm in text. Written English lacks a standard way to mark irony, and several forms of punctuation have been proposed. Among the oldest and most frequently attested are the percontation point proposed by English printer Henry Denham in the 1580s, and the irony mark, used by Marcellin Jobard and French poet Alcanter de Brahm during the 19th century. Both marks take the form of a reversed question mark, “⸮”.
Irony punctuation is primarily used to indicate that a sentence should be understood at a second level.
Source: Ultra Facts