I thought of the same idea, it could be used when creeps want to say, "I'm full", "Carrying energy to storage", "Anyone come carry this energy", "We are under attack", "Please welcome a new creep to our team". Anyway, let's say we don't want to troll other players, those bubles won't be displayed to others, so this feature would be cool to see what is going on in your room. It makkes it more living.