Just wondering about something: how sure are we that this was a troll and not one of the telepathic speech capable muder-ghosts? It's a plot point that the murderghosts are a new thing from a Known World point of view. Maybe the symptom comes from the left field because those in early stages of the Rash can't hear trolls, but can hear murder-ghosts. If that was the case, it would make sense that the story never brought it up before now.
Otherwise, I wonder what effect Reynir's runes will have on her. If they do anything, it will at least help with keeping Tuuri and Reynir at a safe distance from each other, just saying.