Guess it's to aid the americans, irony is often lost on them too.
http://www.telegraph.co.uk/technology/news/6995354/Sarcasm-punctuation-mark-aims-to-put-an-end-to-email-confusion.html
and again
http://www.telegraph.co.uk/technology/news/7035351/SarcMark-inventors-make-thousands-from-sarcasm-punctuation-mark-in-first-week.html
http://www.telegraph.co.uk/technology/news/6995354/Sarcasm-punctuation-mark-aims-to-put-an-end-to-email-confusion.html
and again
http://www.telegraph.co.uk/technology/news/7035351/SarcMark-inventors-make-thousands-from-sarcasm-punctuation-mark-in-first-week.html