Wow, that is such a no-no. Fight choreographers drill into you that fight call is absolutely mandatory every day, even under identical circumstances.
Fighting is dangerous even when you follow all of the rules. I once had an actor have to go to the hospital after a one-in-a-million bounce of a dropped weapon, which had been well blunted for the stage but still managed to cut into his arm. At that point it's in the range of ordinary accidents like tripping over your own feet, but the fighters have to be especially wary of it because there are so many more ways for things to go wrong.
Numerous other safety measures also failed for this accident to occur. Both the one with the sword and the one stabbed failed to note the distance, and the one was swinging much, much too hard if it broke an eye bone. It sounds as if they were either fighting without supervision or got incredibly lazy about it. It needs to be investigated.
I wish HN had a policy to more strongly moderate posts that clearly have absolutely nothing to do with Hacker culture, but I suppose the noise is low enough for the current policy to not really be a problem?