Not hitting things behind thin cover with explosives is not a limitation in the engine, they are using Unreal engine so they would just have to change their implementation.
I am horrible person, so I like to use a krak grenade as a ghetto execution. Enemy goes down -> throw a krak grenade -> do something else. And whenever I do it, I say to my screen 'let's sprinkle some crack on him and get out of here, Johnson!' in my best Dave Chapelle.
