/difficulty command no longer working

Reopened: Can't remove partial xp bars from the "xp -1L" command when you're between level 0 and 1

/difficulty resets after reloading the map!

Infinite potion effects after dying

Entities don't clear lists before reloading from NBT.

Experience levels can be taken away by command, single experience points can't.

Entities (paintings,item frames, minecarts) are breakable in adventure mode