Trait "Sharpening sorrow" removes confusion stack bonus from illusion trait "Cry of Pain". Additionally it makes shatter 2 "Bladesong Sorrow" to not apply confusion.
I have tested it with Traits - Virtuoso 3 3 3, Dueling 3 1 2 Illusions 3 3 2. Noticed that changing middle trait in Virtuoso ("Sharpening sorrow") is the reason of this issue.