I wrote that, didn't I? It's just that I usually envision the FAQ rather as a suggestion or clarification than a rules update, hence my choice of words. Must be because I enjoy my mystic adept
Or has that point finally been fixed? Anyway, no worries here and please, let's not go to that discussion

yes, but besides the freaky spirits like Shadow spirits and insect spirits, free spirits are the only ones I've found who get such a nifty thing. Which scratches it off the list for me.

But I was actually thinking something far more mundane. If a spirit possesses, say, a dog, what happens when you put the dog under a blanket? Or a cowl on a Manservant drone?

Obviously this would have to be carefully thought out with GM approval, and be a full cover type thing (no faces on corpses showing, etc) to work. And GMs would need to be very strict with mistakes to prevent abuse. But I don't see why this wouldn't work. And the part ways should work too, with thresholds for smaller items giving away the face inside a hood, for example.

I am wondering if any of this might realistically affect the spot threshold of 6-Force to spot.

It really depends on how your GM pictures "Obvious Magic". Is it a glow in their eyes, red lines running under their skin, runes on the body? Those could be concealed by a hood and a mask. Or is a strange glowing aura surrounding the individual? A lot more difficult...
A matching costume might at least raise the threshold again or give a penalty to the perception check.