S rank hunt mark Ker is not displaying a buff/debuff related to an abiliity properly.

Frequency: Always
Monster name: Ker
Zone: Any Endwalker zone with hunt marks.

Steps:
1. Engage the hunt mark after it's been spawned from killing the Ker Shroud mobs that occasionally appear after the demise of a different Endwalker S rank.

2. Wait until it casts the spells Whispered Incantation or Mirrored Incantation.

3. If you have the "Display only detrimental effects you inflict" option toggled on, you will not be able to see either effect on the enemy. This is problematic in the case of the latter spell, as you need to be able to tell when it loses the effect to determine what side of it is safe for its Internment mechanic.

According to the combat log, the effect is classified as a detrimental effect, which is presumably it is being hidden. This runs contrary to most enemies in general as mechanic altering effects are generally classified as beneficial effects, and thus can be seen regardless of the aforementioned option being toggled.

That makes sense. I can still see it when I make it my focus target so I didn't notice.