A Practical and Authoritative Guide to Contemporary English. 1996.
Page 261
Because the immediacy of chat rooms resembles that of speech, they are the most informal of all modes of electronic communication. Because of their relative formlessness, chat rooms may be the least efficient way of using your computer to communicate.
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Informality
Because certain forms of E-mail are characterized by a rapid give-and-take that resembles conversation, they tend to be more informal in tone than conventional print writing and the more institutional forms of electronic messaging, such as corporate reports. In fact, these conversational E-mailers have developed a variety of practices to sustain an informal tone while at the same time saving keystrokes. E-mailers commonly use contractions and abbreviated expressions. They often omit pronoun subjects, as in don’t know for I don’t know, depends for it depends, and glad you asked for I am glad that you asked. Another common practice is the use of “eye dialect” spellings, as in gonna for going to, gotta for have got to, and thru for through. Many people use acronyms to stand for commonly used expressions or to indicate attitudes and emotional responses. These acronyms are usually capitalized. Here is a selection of commonly used E-mail acronyms:
