The Pahn Kahl Religion
In the Siri section, she mentions the Pahn Kahl religion, but she doesn't know what it is. This happens numerous times in the book, people getting confused about whether the Pahn Kahl are just Hallandren or being unable to describe their religion.
If you're curious, the Pahn Kahl are nature worshippers who focus on the storms of the Inner Sea as a manifestation of their unity of five gods. They believe that all Returned are men who deny the power of the gods and are forbidden entrance into heaven, yet are otherwise just men and not sinners worthy of hell—so they're given a chance to come back to have another try at life, to try to find belief this time.
Anyway, the purpose of having people so confused about the Pahn Kahl was to try to make readers vague about them in the same way. In this case, I want the reader to feel that the Pahn Kahl are unimportant, like the characters do, which is exactly the reason why the Pahn Kahl are so annoyed in the first place. If Hallandren didn't take them for granted so much, there's a good chance they wouldn't be so inclined to rebel.