In Brother's Keeper,
Dean kills Death with his own scythe instead of killing Sam as Death is insisting at the time.
Then, in Form and Void, Billie says to Sam
"... The old death thought it was funny. But now there's one hard, fast rule in this universe..." (my emphasis)
So, my question is, who is making the rules?
It has been said that reapers rarely gather in large numbers, only a few dozen showed up for Death's rising in Abandon All Hope, but Billie implies that all of them are on board with the rule. That implies consensus or a new boss.
Additionally, her use of the word old is odd if a replacement hasn't been appointed. Why make a distinction between what was and what isn't?