@daredevil I'm sorry but you seemed to have missed what I said about people actually seeing the person they are firing at. I said that if you have seen the person there then you should by all means fire at them, even through walls. But if you are just randomly shooting through a wall on the off chance that someone is there, that is not beneficial gameplay.
Your question of "how can we block it" applies to most of the rules on the servers, right? How can we block people from nade switching, how can we stop people from harassing other players. I mean the list goes on. All that can be done is enforcing these rules.
It isn't hard to randomly shoot through to the other side's spawn in a hope to kill enemies. All that does is take away from the gameplay.