I can’t see obscure punctuation like the ‘snark’ finding a place any time soon. People seem to have enough problems with the punctuation we already have. Besides, sarcasm symbol would instantly reduce the humour in the sarcasm – it’s a bit like explaining a joke.
Another mark, now obscure, is the point d’ironie, sometimes known as a “snark.” A back-to-front question mark, it was deployed by the 16th-century printer Henry Denham to signal rhetorical questions, and in 1899 the French poet Alcanter de Brahm suggested reviving it. More recently, the difficulty of detecting irony and sarcasm in electronic communication has prompted fresh calls for a revival of the point d’ironie. But the chances are slim that it will make a comeback.
Although in the written English language there is no standard way to denote irony or sarcasm, several forms of punctuation have been proposed. Among the oldest and frequently attested are the percontation point invented by English printer Henry Denham in the 1580s, and the irony mark, furthered by French poet Alcanter de Brahm in the 19th century. Both of these marks were represented visually by a backwards question mark (unicode U+2E2E ⸮ reversed question mark). The character can also be represented on Windows by using the Alt code 1567.