The roleplay angle I would take at this point is that newer members of the Deathwatch more than likely keep to their own trappings.  As the Space Marines grow closer together and feel more at home among the Deathwatch they might abandon those trappings and embrace the unity of the Deathwatch.  Of course some never leave their home Chapter or world behind, perhaps holding onto those symbols as well.  At this point, being a newer group, the Sergeant probably overlooks and expects much of what he sees.