Lex Manos

Sorry, thought you meant "I could not find a instance of that entry in a vanilla leval.dat" not "It's there, but I suggest it not be"

Actually, there is in single player worlds, as the level.dat contains your player's entity as well. And this value is stored on all EntityLiving
Personally, I believe that Players should just have this functionality disabled as they are controlled by a player and shouldn't have items swapped without them wanting it.