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.
Squick: Angela Carson's death. She is killed by her reflection as it grips its jaw and slowly pulls its mouth apart, causing her to bleed profusely.
And Gary Lewis'. The mirror kills him by slashing its throat, causing him to die. Made so much worse by the fact that we don't get a murderer's hand to obstruct our view, like we would if it was another person doing it.
What an Idiot: Michael removing the paint on the mirrors and turning the water on throughout the house, causing the near-death of his mother and his father to get trapped in a Mirror Dimension forever.
The implication was that his Evil Mirror Twin was making him do these things so as to let the demon into their home; pay close attention to the scene where it turns out Ben missed one tiny reflective spot on a doorknob, and what happens to Michael right afterward.