Sentient corpses in the refuse pile will spook them. Also, these corpses will spook your dorfs as well, causing them to get stressed (every season they encounter the remains of a sentient they will have a thought about seeing it die, for each sentient encountered). Moving the pile and having walls around it will help somewhat. Another way is to dispose of sentient corpses completely by dumping them into a hole (with a refuse pile at the bottom to help degrading them) or into magma, or storing them in a separate sentient only pile (which is a royal pain to set up). I've set up half a quantum stockpile for sentients which dumps the remains into magma. However, each and every sentient species you encounter will then have to be manually excluded from the normal pile's corpses and body part refuse sub categories (at least). The sentient pile's settings has to start with disallowing all because FBs/Titans are in hidden categories, and you typically want to harvest those -> send them to the regular pile). After the start, the same species as excluded in the regular pile has to be added to the sentient one. I process species as I encounter them. Also note that dwarven enemy corpses are buggered, so they are considered to be of the overall Corpses category, not the Refuse Corpses sub category (dwarven undead and necromancers end up in this category). Also, at a MUCH later stage, denizens of hell are considered sentient but of hidden categories, like FBs. I ended up dumping those into magma.