/ignore works for ICO, but not ingame messages -- your confirmations were telling you that the person was being ignored in the ICO channels, which you are in fact still connected to while in games (that is how you can whisper people not in the game or send messages using /friend, etc..)
You can't /ignore people inside the actual game.
If I'm wrong about anything I just said, Annatar should correct me soonish.
