Most probably my translation is bad because I heard it very long time ago, but I think the driver did not want the kid with the broken leg to yell so loudly and alarm pedestrians charging them against the driver. So he said to him that his injury was not so severe as the other kid so he needed to be more silent than the other respectively. Of course dead people do not cry out while being dead and there was the joke. But the whole situation in reality would be completely different.
Anyhow, I understood Faile’s joke and I do know it was in a spirit of fun, but I also considered that on this forum, there might be many people who have many different disabilities with different degrees of severity.
Maybe they do not talk in a strange way, maybe they are not mentally retarded but still have a trait or two that others may make fun of, and they may recall being laughed at, which is really a very bad feeling.
