These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Fan Discontinuity / Dolled-Up Installment: The Requiem expansion according to many fans. The ending of Black Plague is self-sufficient, and Requiem feels more like a weird Portal ripoff with tacked-on closure to some side plots, than a proper Penumbra game. While preserving the horror and Mind Screw atmosphere of the first two titles, the absence of a real physical threat to the player kills what little interest there could be in this purely puzzle-solving adventure.
Fridge Horror: Overture alone has at least three areas of small abandoned rooms, where people were forced to stay and live underground from a span of weeks to entire years. All that in horribly cramped conditions, with a lack of any appropriate space and furniture for long-term habitation. Red's story is a particularly horryfying case of this...
Hell Is That Noise: Happens nearly constantly. Still think you won't get scared? Think again.
Phillip also agrees to willingly incinerate Red at the end of Overture to free him of his suffering. But after he hears Red's gruesome last screams and pulls the key he needed from Red's ashes, he nearly suffers a Heroic BSOD.