Hold up. The ENTIRE point of Shadow is that he's a separate, ambiguous figure NOT associated with the Blackquill. Xavier should NOT be able to identify Shadow as a member of the Blackquill. From the dialogue, he's never met Shadow. The only way he could possibly recognise him is see him fighting with knives and crossbows, but he's fighting with swords and bows. Xavier should not be able to pin anything on Shadow outside of what he's been showing. Shadow is a mercenary who owes his life to King Harry, and so serves him faithfully. That's who he is. Not a member of the Blackquill.