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.