Getting back to the original point-- which was about courtesy, not tactics...

1. Friendly insults-- with friends-- are entirely different than with people you really don't know. I doubt this is just an American thing, tho the best quote is from that very American western novel, "The Virginian," in which the main character says, "When you call me that, smile." Because it is a remark/insult which could be very common among friends, but which would cause a gun-fight if used with non friends.

And I agree with Grief8-- many people are a lot "bolder" in front of their computers than they would be in person, regardless of what they might say.

2. If there is a cultural difference, maybe it's the European guys are quick to cross the line of "familiarity" and treat strangers as though they are friends-- friends whom they can belittle and make fun of. This is interesting, since if Americans are not being called "oversensitive" they are generally being called rude or boorish.

Incidentally, this line, "you're being too sensitive" is a common reply of the oaf who has crossed a line and does not like being rebuked for it. No, they aren't being "too sensitive." You are being an oaf. Because...

3. Remarks like the ones we are talking about here really are another way of "bragging" aren't they? Like saying, "I'm smarter than you- stupid." Not really very funny, or friendly, are they. Just trying to pose as a superior being-- because of a guess made at a keyboard on a game. Yes, it's a game and we should get back to it and have fun, and not take our success too seriously, since it really does not "prove" anything very much about life or history or anything else...

Other than "jerk" is something which can appear in all cultures, even if the language is different.