when using a lead on a named mob (say, a llama, or cat) and then removing the lead, the lead will have that mobs name in the lore, even if the mob is alive and the lead was removed by a player and not dropped upon the mobs death.

this makes it so the leads cannot be stacked.

is the lead is subsequently used on an unnamed mob, the lore is removed and it can be stacked again.

it's not a huge game breaking thing, but is a bit annoying sometimes.

There's a problem here the same as why I didn't made something like #13 either since the beggining. When the item is dropped, the game does not know yet that the mob is dying, so I can't check if the mob is dying as well as I can't get it's proper death message (I don't remember if it returns the default one or the one as if it died from the previous damage it took)