For a version of function defined as 'could be manipulated by an ancient evil'. They do not let that one out in public around mortals.
When compared to the "head explodes" of looking at a mook angel's pistol or being stuck meditating on your horror as you scramble for some amount of sanity it does. Frankly I'm skeptical of the idea that trauma inherently makes you resistant to further exposure without actually breaking people in a functionally relevant way.
It's like burning your hand to charcoal making your dex check to scoop up molten metal with your fingers easier. That really seems like it should be a cascading failure mode instead of resistance training to me.
Even at its lightest the consequences have always been shown to be immediate, disruptive, and an ongoing issue that takes actual effort to manage.
I'm not saying it should be absolutely impossible for anyone to do, but when everyone we encounter is capable of using the sight while engaged in complex magical combat without missing a beat that seems like a sign something is wrong.
Also, wasn't this the Sight wizard?
Antonio Verdi," Morgan mutters under his breath, sorting the man in some kind of mental file and putting a stop to the conversation before your friend can creep out Carlos anymore. "How the fuck did they get him, for that matter why? In and out of the Halls most weeks, but he didn't have clearance for anything major...." The next words, whatever they may have been, die on his lips. "A messenger, someone who was known to have good reason to cross the wards at odd hours coming or going.
He's the guy our magical support followed the ritual back to, and he was apparently sane enough to act as a subtle messenger from the halls. I'd think that wizards of all people would know would notice the signs of someone going violently insane from sight abuse. Which would make for a poor smuggler.
If he can pretend to be normal well enough to fool experts and handle sensitive tasks then I'd say he's plenty functional.
Either that or the council saw no problem with a raving madman wandering into and out of their fortress at odd hours of the night carrying random odds and ends.
— Gates to the Hidden Halls, 2 am—
Wardens: " Hey Antonio, heading home?"
Verdi: *Twitches and jumps like a meth head while nervously twisting his hands* "Yes Yes, must get home with my papers before the shadows start bleeding eyes into my soup again"
Wardens: "Well we wouldn't want to keep you then, have a nice morning"
Edit:
Or more succinctly, being an unspeakable mind bending horror to behold has been a problem for Molly more than anyone actually looking at her. Almost literally "Ha Ha, by flaying my brain with your blasphemous visage you've fallen right into my trap".