When you first start, you get rated 1200 but your rating jumps in very large amounts (like 100 pts) for every game you win or lose. It's only after you've played more games (maybe ten?) that your rating goes up or down by a more sensible amount. This lets the ratings for a new player get into the right ballpark faster. I looked at your live chess games, and I think I see one you mean, and he only has six games under his belt.
Resolved: Opponents Rating Jumps after Loss
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Ok, what the heck?? The last 2 times I've lost a game to a 12xx rated person, right after the "you lose" screen, his rating jumps up to 1300+. It's like saying "ha ha! I was really way better than you from the start ... you just didn't know it". Why this annoying behavior?