I always thought that more explanation should be added behind the monsters link faces. They are always so random. And i think that the reason why they do not show emotion would be to make it easier to kill them. Killing a monster and killing something with human emotions and reactions that the player could identify with would produce different effects. It's like, "oh, look a goblin thing" *slice* and thats that. But like in Oot when I shot down gerudo girls with arrows they made a little yelp which made me, as the player, feel different about it.