At first, I didn't pay much attention to the idea of the "sarcasm mark" that's been making news recently. It just sounded like a joke or scam, and since it's for sale, that kind of lends to that theory. All English fonts in the world would need to change, and all keyboards too.
Then I started to think that maybe they're onto something. Sarcasm in DVD subtitles often seems to be indicated with a bracketed exclamation mark "(!)", which is relatively clear in context. Using a sarcasm mark in the same way could become standard if people adopt it. The trouble is that in the meantime, we don't have any way to directly type such a mark in plain text. So the transition period is going to be difficult.
Mokalus of Borg
PS - The sarcasm mark for sale does look a bit like a bracketed exclamation mark.
PPS - There's a picture in the linked article.