A lot of the signal in spoken English is carried by tone of voice and emphasis. Which confuses people from cultures where emphasis is not part of the signal, much as English speakers are often confused by tonal languages.
Written English is more formal presumably because it has to get by without that part of the signal.
Written English is more formal presumably because it has to get by without that part of the signal.
http://en.wikipedia.org/wiki/Eats,_Shoots_%26_Leaves