I agree with you that it doesn't make sense, and think it's just a textual error — i.e. it should be Karhold. As you point out, having ravens that would fly to the Dreadfort would also be incriminating. Some people think it's intentional, though I think you have to come up with a pretty bizarre backstory to get the conversation to make sense that way.
It Rhymes With Meek replied to Hmadkour's topic in The Winds of WinterActually, in ACoK before Catelyn released him Jaime literally told her "I flung him from a window."