Quest items do not count towards the inventory limit (or didn't in D2:ED, anyway).
You may be right about that. But I really believed at one point quest items were counting as inventory 'weight' when I stopped to evaluate my weight situation one time when I couldn't loot all the contents of a chest. I may have just made a mistake on that conclusion.
In a world with levitation strong enough to keep huge rocks floating in the sky, I don't have a problem with levitation strong enough to control a fall. Also, the slayers were formed to exclusively go after opponents that can fly, so the ability to take a fall would have needed to been one of their first concerns.
It does make some sense from a story standpoint. Still, I'd prefer falling damage to be in a game like Divinity 2 (as annoying as it sometimes can be) because that mechanic can provide the appropriate tension for overcoming different types of challenges in games like this.
