When champions such as Nocturne have passives that where the CD is reduced by certain actions, the flash that demonstrates the reduction is appearing on the Q skill instead. It may be just Nocturne but I think it happens to Ziggs as well. The passive CD is reduced as normal but the flash is on the Q icon.
HOW TO REPRODUCE:
-Select Nocturne or Ziggs
-Use up your passive by autoattacking
-For Nocturne, simply autoattack again and watch the Q ability icon. For Ziggs, use an ability.
-Ordinarily the passive icon will flash to signify the CD being reduced. However, the Q icon will flash instead.