This is not about navigation markers. This is about the gray text below some quest objectives in upper right corner of screen in default interface configuration. The text starts with "Hint:"
For example, I just spoke with 2 townspeople, and from the dialog, it seems I must investigate the stables. But there is hint text flat out telling me to check the stables whereas the quest objective is: investigate the mystery. It kinda takes the fun out of these quests to have constant insta-spoilers.
I've dug through a few different settings screens, but of the options I could comprehend and wasn't afraid to fiddle with, none seemed to fit.
Best Answer
You can't remove the hints exclusively using the vanilla UI (which means on PS4 you're lost).
However, these are typically the exception. Maybe 1 out of 20 or 30 quests actually uses those hints.
Also, something you probably didn't notice, these hints usually only reveal what your character learned. They won't provide you out-of-character information (at least not more than quest markers).
In your specific instance, one of the townspeople mentioned the stables, which triggered this hint popping up. They're often more like "notes" rather than "hints", so you shouldn't worry too much about them spoiling anything (because they don't). They'll only appear once you learned something. of course it's a different thing if you didn't pay attention or interpreted something differently.