Given past animosity, is it unusual for a Dornishperson such as Edric Dayne to be squiring for a Stormlander like Beric Dondarrion? Is such a thing a sign of old wounds healing during the reign of King Robert?

Not that unusual – the stony Dornish and Marcher lords intermarry fairly frequently to settle vendettas, but it doesn’t work out any better than it does for the Brackens and Blackwoods. Edric’s squiring is part and parcel of the marriage alliance with Allyria.