Question mark
The rhetorical question mark or percontation point was invented by Henry Denham in the 1580s and was used at the end of a rhetorical question; however, its use died out in the 17th century. It was later revived in modern-day society by Matt DiRoberto. It was the reverse of an ordinary question mark, so that instead of the main opening pointing back into the sentence, it opened away from it. This character can be represented using the reversed question mark (⸮) found in Unicode as U+2E2E. The percontation point is analogous to the irony mark, but those are even more rarely seen.
Sarcasm
Though in the English language there is no standard accepted method to denote irony or sarcasm in written conversation, several forms of punctuation have been proposed. Among the oldest and frequently attested are the percontation point—furthered by Henry Denham in the 1580s—and the irony mark—furthered by Alcanter de Brahm in the 19th century. Both of these marks were represented visually by a ⸮ backwards question mark (unicode U+2E2E). Each of these punctuation marks are primarily used to indicate that a sentence should be understood as ironic, but not necessarily designate sarcasm that is not ironic. By contrast, more recent proposals, such as the snark mark, or the use of a following tilde are specifically intended to denote sarcasm rather than irony. A bracketed exclamation point or question mark as well as scare quotes are also sometimes used to express irony or ironic sarcasm.