On eHell, when somebody says outright "you were rude" or "that's rude", I always find it a little confrontational. In real life, we're more diplomatic than that! I'd prefer to cushion my opinion and say "I feel that was a little rude for X reason and because of Y", or something like that. I don't think it's entirely up to me to judge what's rude and what isn't - if these situations were so easy to judge, we wouldn't need eHell! So I think being that direct about it is definitely a difference I've observed. Then again, perhaps others do say "You're rude!" in real life as well as here? I try to never be that blunt with my opinion though.
One thing that's common both here and in RL to me? Generalisations. I really can't stand it when people make broad statements about a group of people - presenting something as fact, when what's actually true is sometimes, or in their observation. I know some people feel that this inferred when they make a statement, that we know they're not saying all. Well, I don't know. You might really think that all people in X group are like that! (Because unfortunately, there are prejudiced people out there). In RL, I think somebody would be called on it quite quickly, and it's the same here. Unfortunately it's something we all do a lot of, by accident usually. Somebody else will usually say "Hey that's not always true, I'm X and I'm not Y!"