I can't agree, only becaase, I can also nerf an NPC if the balance isn't right without the players ever knowing it happened, I can't do that to a PC without someone crying foul. If I screw up as a DM and the only thing that gets hurt in the process is my pride, I can handle that, if I suddenly have to talk to a player because a decision I made is going to screw their character concept over, then I have to deal with possible hurt feelings, sudden campaign shift (you wake up and find Bobby in the shower syndrome), and maybe even a player leaving the table, I don't want that. Too many DMs have forgotten that they weild power that players just don't have. (That's why they're called Dungeon MASTERS.

) A half-celestial PC is verbotten, a half-celestial NPC is fine, why, I can control the NPC, the PC is out of my control. I can suddenly have the NPC 'go way' if they break balance, I can't tell a PC to 'just go away', does that make sense?