In e-mail from Microsoft employees, you may find a stray J like this one at the end of a message from Rico Mariani. Some of you might see it; others might not. What's the deal with the J?
The J started out its life as a smiley-face. The WingDings font puts a smiley face where the letter J goes. Here, let me try:
<FONT FACE=WingDings>J</FONT> results in J. As the message travels from machine to machine, the font formatting may get lost or mangled, resulting in the letter J appearing when a smiley face was intended. (Note that this is not the same as the smiling face incorporated into Unicode as U+263A, which looks like this: ☺. Some of you might see it; others might not.)
I recall a story (possibly apocryphal) of somebody who regularly exchanged a lot of e-mail with Microsoft employees and who as a result started signing their own messages with a J, figuring this was some sort of Microsoft slang. The Microsoft employees who got the J-messages scratched their heads until they were able to figure out how their correspondent arrived at this fabulous deduction.
And now, the mysterious J has come full circle, because some people use it ironically, intentionally just writing a J without setting the font, in the same way people making fun of "leet" writing may "accidentally" type "1"s (or even more absurdly, the word "one") into a row of exclamation points.