<flame>
Your father was a hamster and your mother smelt of elderberries!
</flame>
You'll even see this with an HTML-style modifier:
<flame intensity="100%"> You seem well-suited for a career in government. </flame>
Hackers also mix letters and numbers more freely than in mainstream usage. In particular, it is good hackish style to write a digit sequence where you intend the reader to understand the text string that names that number in English. So, hackers prefer to write `1970s' rather than `nineteen-seventies' or `1970's' (the latter looks like a possessive).
It should also be noted that hackers exhibit much less reluctance to use multiply nested parentheses than is normal in English. Part of this is almost certainly due to influence from LISP (which uses deeply nested parentheses (like this (see?)) in its syntax a lot), but it has also been suggested that a more basic hacker trait of enjoying playing with complexity and pushing systems to their limits is in operation.
Finally, it is worth mentioning that many studies of on-line communication have shown that electronic links have a de-inhibiting effect on people. Deprived of the body-language cues through which emotional state is expressed, people tend to forget everything about other parties except what is presented over that ASCII link. This has both good and bad effects. A good one is that it encourages honesty and tends to break down hierarchical authority relationships; a bad one is that it may encourage depersonalization and gratuitous rudeness. Perhaps in response to this, experienced netters often display a sort of conscious formal politesse in their writing that has passed out of fashion in other spoken and written media (for example, the phrase "Well said, sir!" is not uncommon).
Many introverted hackers who are next to inarticulate in person communicate with considerable fluency over the net, perhaps precisely because they can forget on an unconscious level that they are dealing with people and thus don't feel stressed and anxious as they would face to face.
Though it is considered gauche to publicly criticize posters for poor spelling or grammar, the network places a premium on literacy and clarity of expression. It may well be that future historians of literature will see in it a revival of the great tradition of personal letters as art.
:Email Quotes and Inclusion Conventions: ========================================
One area where conventions for on-line writing are still in some flux is the marking of included material from earlier messages — what would be called `block quotations' in ordinary English. From the usual typographic convention employed for these (smaller font at an extra indent), there derived a practice of included text being indented by one ASCII TAB (0001001) character, which under Unix and many other environments gives the appearance of an 8-space indent.