Red glint in Jean Françoise only available if you look at the full body animated portrait.
Aside from the small description Musketeer Mage that is his epithet. I have always thought there was little more to him.
My theory is that JF is not human, but rather he is a Dhampir - A half-vampire and half-human hybrid, having the strengths of the vampires, but none of their weaknesses. His innate ability is that he is immune to drain-life type ailments, which are, not surprisingly, used by the vampire heroes (Victor, Valeria, etc.)
Red glint in his eye might be a reflection of the vampire side of him surfacing briefly.
He may also be a hunter of vampires, he is a practitioner of fire magic, while may not outright kill vampires, but could slow them down enough so his rapier, which could be made of silver delivers the final kill.