Lately I've been futzing around on a vampire-themed MUX, playing someone who's extremely gregarious, outgoing, friendly, et al; I'll go and start conversations at random with people about any ol' thing. This is completely and utterly opposite to how I am in real life, where I'm quite loth to do anything like that - generally due to not being able to think of anything terribly interesting to talk about, not having an idea of what the other person is like, being scared witless by the prospect of strangers, etc. I suspect that the main difference between the two situations is that I have more time to think about what I'm going to say (and can generally correct any muffs I make before they get uttered), and the layer of social insulation engendered by virtue of being online but also knowing that the other people there are on precisely to interact.
There are some other odd things going on there as well. I generally tend to pick up on the social cues that are intentionally broadcast by people in the midst of what they're describing or acting out - something I'm kinda rotten at IRL. One of the weirdest things I've noticed, though, is that while I pick up on the in-character cues, I utterly miss a fair amount of the cues in the out-of-character conversation - the general blathering about things not related to the plot of the game. I've come up with a few theories, but none of them seem particularly satisfying. One is that because it's a game setting - and further, interacting online where expressive comment is at a premium - there are semi-formalized rules for interaction that are greatly stripped down from how "real-life" interaction works and are thus easier to pick up, whereas the OOC banter has no such restrictions. A related theory is that because the amount of communication is limited, the amount of available information is very small and it's thus possible to know exactly what's going on and is something I can process; for OOC, the same reasoning as the previous theory.
One of the more amusing things is that while I know there are some people I know on there, I have absolutely no idea who they are, nor they me - as far as I know, at least. I find that perversely fun.