I've been coming through the XML files and I found two abilities that I don't think do anything.
1. A_Influence, which is used by the faction trait "Influential" (Magnar and Pariden) claims to increase the area of influence by 1 tile. This does nothing. Area of Influence/Zone of Control/Kingdom Boundaries are all tied to ZOCMinRadius/ZOCMaxRadius.
2. A_Learning is tied to the "Stupid" Sov trait. This trait is supposed to make it harder to learn spells. I did not see a change in spell learning time when I took this disadvantage. The ability A_Spellpoints IS used, however, and it DOES change the learning time of spells.
I also know of some other XML bugs:
1. The Arrogant faction trait decreases champion recruitment costs by 20% instead of increasing them by 10% or 20%. (For reference, the Sov's penalty trait increases the cost by 15%.)
2. There are no legendary arm greaves.
3. The Summon Demon spell is missing a picture because of a comma: <Image>DemonicAlly_Painting,png</Image>