I'm pretty much the same, since I don't think before I write. And I also don't think before I speak
But since the facial expression and emphasis is missing, people take me too seriously most of the time or think of me as a pretty serious person xD People always seem different in the internet then when you meet. I think I would hate my best friend with a passion if I only knew her online
Same goes with a lot of my friends or people I met after getting to know them online.
I also think that, if I roam around english sites my limited ability to use the english language distorts my character additionally. Since I can't transport the way I speak in my native language just like that ^^
I don't act different conciously, but NO ONE is exactly the same on the net imo, at least they don't seem to be. An avatar isn't a good replacement for a face after all