I don't consider any of these to be good reasons. First of all, Norman loves the walking dead and his character and wants to see this project through till the end. He has even been quoted saying that if he gets killed off he will burn down his trailer in protest. Second of all, I feel that the moral compass thing is just stupid. At one point or another each main character has been the voice of reason or "the moral compass". They are not going to kill Daryl off simply because he has a conscience. And your third "reason" is pointless. He is starting to really care about Alexandria and its people and he was torn between following Rick and wanting to be there to protect his new home. He did go back to Abraham and Sasha to try to get the herd away. They are not going to kill him off right when his character is really starting to open up. I don't feel that they will make the same mistake that they did with Beth, they regretted immediately that they killed her off right when character was beginning to blossom. And honestly, he is one of the fan favorites. And I am sure they are well aware of this and the backlash that would ensue if he was senselessly killed off.