Interesting question. I have no idea what y'all think it's my online persona, but I don't think it's very different from who I am IRL.
I'm not very conversational, I just say a lot of one liners and witty comments. Or at least that's what my family & friends say.
I don't consider myself shy, but I'm not an extrovert by any means. I would probably listen and stay quiet until I hear something that is interesting or can add something to a conversation.
I don't think that I'm rude or arrogant or intimidating, but a lot of people say that's their first impression. On the other hand, I think most people give a "fake" first impression (i.e. try to look friendly or smart or interesting) when in reality they aren't like that.