peterhassett asked: "The gangling steward [Wick] backed away, his hands upraised as if to say, Not me, it was not me." "Jon reached for Longclaw, but his fingers had grown stiff and clumsy." That's two characters apparently not in control of their bodies -- in the same paragraph. Maybe it's not Bloodraven, and maybe it's nothing at all, but I think there could be some support for skinchanging in that mess.
This is just poetic license. Wick’s reflexively reacting to being looked in the eye by someone he just stabbed — surely we’ve all seen people in fights who land a punch, draw the attention of whomever they just struck, and instantly back away all “who, me?!” — and Jon’s losing control of his extremities because he’s in the process of bleeding to death. Skinchanging doesn’t enter into it.