The showing of eyes and the things that illustrate the concept of duality are usually normal and no secret sign.
But there is one big HOWEVER. There are circumstances joined with a hidden purpose that can make these normal things a secret sign. "Satanic" or "Hellish indications" or "signs" must not be too suspicious and therefore they only consist from normally-occurring things, but in some special circumstances and order that indicates their "different-than-normal-only" purpose. Its that simple lol.
I fail to see the distinction. You've already shown numerous examples where it was clear the eyes were focused on solely for dramatic or comedic effect. In the above you've carefully chosen 3 movies where duality was the central theme, so such a portrayal is to be expected. As far as that goes, there's a mirror scene in practically every version of Doctor Jeckyll and Mister Hyde. It's common enough in other movies and comics to qualify as a trope of it's own, separate from the even more common "inner demon" cliche'. Seriously, I'm surprised you aren't going for the more obvious stuff like The Hulk. How about Ghost Rider? Now there's a hellish person for you.