Hints are an optional aid that can be switched on and off in The Hub.
Left of the hand on the wall is a cage with a ghastly face inside it. Interacting with that face toggles hints. It sits between the hand, which changes the eyeball you start a run with, and the Mirror, which is your own reflection and has a full dialogue tree.
This wiki records where hints are toggled but not what they actually change in a run. Nothing in the guides, forum threads or the manual read for this page described their effect, so that is still unrecorded.
Compiled from what this wiki already says on The Hub, Eyeballs, Mirror. No new facts were added.
The wiki's owner has never used the hint system, so it remains unrecorded here by anyone who has.