I just had a thought about the dusklings. Lalli mentioned that their hide only offers partial protection from light. This could mean that they are exposed to very small doses of sunlight on a regular basis. I'm thinking along the lines of not enough to make them retreat back to shelter, but still enough to have some kind of effect, like some kind of "getting a sunburn on an overcast day" phenomenon.
Brief exposure to sunlight was enough for a dog's mind to be restored to an extent in Chapter 7. I'm wondering if the regular partial exposure to sunlight had a more gradually acting version of this on the dusklings, and they have white speechbubbles because they accidentally got rid of whatever the Rash does to the mind over time.
Pastor Anne wasn't being hurt by sunlight too if I remember correctly. Maybe the more corrupted by the Rash the mind is, the less resistant it is to sunlight? The dusklings seem pretty intelligent, with their sun covers, forming packs and ability to recognize danger.
I was also thinking... given how exposition to the sunlight for an hour can replace the usual decontamination process - it all seems to be connected to the fact that sunlight weakens the Rash. What if when it takes over completely, it makes the person "think" that the sunlight hurts? Kind of like the parasites that alter their hosts' behavior patterns, making insects climb up to exposed places so the parasites can infect birds, or making insects drown in the water so the parasite can reproduce, etc etc