I’m less shy online, so I’m not as passive in my posts as I am when talking to people I don’t know that well IRL.
Otherwise, this is me.
I tend to write exactly like I talk, which includes things like elipses (…), which signify pauses or breaks when I am talking something out. I often work problems out by talking them out to myself, although mostly silently or subvocally.
I also have two different “voices” IRL and OL. A relatively educated, polite voice, which uses far too many commas, and larger, more important and more formal-sounding words. And then I have my “fight or flight” voice, which is very short, abrupt, and often very profanity laden. And, I am told, pretty scary when I slip from polite speach like I write here, into “Fk you, you stupid dumbst gdamn motherfker, don’t make me stick this in your fking worthless heart you fking pile of s**t!”
(edited for IMHO by Una)
Or words to that effect.
Online I speak pretty much like I AM. IRL I edit myself constantly because I somehow feel that’s what is expected of me. Online I’m judged solely by my words and not my appearance, which has varied greatly through the years. I have always been considered probably pretty smart but maybe not necesarily cool. Well endowed but did not possess the loose morals that were expected to go with “them”.
Online, I am what ever I say I am.
I must be the same, because one of my friends was “lurking” here and said that she wasn’t paying any attention to the usernames listed on the left hand side of the thread. She was reading one of my posts and said to herself “this person sounds just like Cheri!” Sure enough, it was me. So, I guess that answers this question for me.
Wherever I go, I’m still me. I overuse ellipses (on a bad day, I sound like…Captain…James…T…Kirk) and parenthetical comments just as much IRL as I do here–and I speak in acronyms, as well (hazard of being an engineer). The only things you loonies miss out on are my fake accents and over-the-top ranting tones. 
I “talk with my hands” alot IRL, which is obviously not possible here. I’m also more sarcastic, which is hard to do online without ticking people off, so I try to avoid it.
IRL I’m the one making the jokes. I am very punny and always have a quick comeback. Online I seem to be serious. Maybe what I need is more online straight men to feed me lines.
::mustn’t analyze last line::
I’m sarcastic and irreverent online and IRL. I don’t know any other way to be, which is why I occasionally find it necessary to explain myself, but that comes with the territory both online and IRL.
I’m more well-spoken online. Probably because I’m a writer. There’s time to think things out before you say them.
In person I’m not nearly as witty, and my agruments are more emotional than logical.