This was required when we linked each framework as its own thing, which we do not do anymore, and if we do go back to this system, we can simply have symbols public by default.
We always undo the last edit without any coalescing so the user can be sure that ⌘Z only undos the last thing they did. For redo though this makes less sense, although it does break symmetry, i.e. pressing ⌘Z n times will bring us back again by pressing ⇧⌘Z only n-1 times.
