The more I think about this I think that Mrr has hit on a really good question; generally in balladry and folklore the dead don't come back to haunt the ones who loved them except for overpowering reasons. So in Sweet Willam's Ghost he comes back to reclaim the plighted troth and thus gain release for his spirit, while in The Unquiet Grave the dead lover (who is either male or female in differing versions) is prevented from resting at peace by excessive mourning. The living are warned not to kiss the dead as a friendly piece of advice.

So The Suffolk Miracle on the face of it doesn't make any sense; and neither do those other songs of revenants such as She Moved Through the Fair or the versions of The Grey Cock as sung by Cecilia Costello where the night-visting lover is a ghost.

I think that Professor Child had quite a lot to say about underlying story of The Suffolk Miracle, and I've seen references to an article by Hugh Shields (which I haven't read myself) suggesting that the revenant variations of The Grey Cock are a late embellishment.

Mrr has raised some really interesting questions about dead spirits here. There is a lot going on in some of these ballads which could tell us about old beliefs.