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.
Alternate Character Interpretation: In Eleusis, Mark joked that his character is actually a homicidal maniac hunting for a blacksmith and dirt. He further jokes the antagonists and villagers are just trying to stop his reign of terror and are innocent townsfolk.
He actually has this assumption for most of the protagonists he play as who has a mysterious past/past they can't remember. Sometimes he's correct, and sometimes he isn't.
Broken Base: According to YouTubers who dwell in their Fan Dumb and Hate Dumb, you're either a Markiplier fan, or a PewDiePie fan. Weirdly enough, they've thrown Captainsparklez into the mix as well, for reasons that are not entirely clear.
From late-2013 onward, there's an increasing number of fans who feel that Mark overacts a lot more than he used to, and think that his earlier videos have more genuine reactions and much calmer commentary. Others think he's better than ever, or that he's as good as he ever was. The fact that he now edits in images and words into his videos to make more jokes instead of just relying solely on game footage just makes this worse.
He went through this himself with Vanish by the time of his final playthrough of it. He explicitly says that the game is so unfairly difficult that after so long it's tense atmosphere becomes frustrating rather than scary.
The longer he played Evil, the less impressed he was. He didn't even so much as flinch at a loud and sudden screamer or any of the attempted jump scares for that matter, and outright laughed at the twist ending.
In his play-through of Penumbra, he immediately hated Clarence for making him kill Dr. Swanson, the only person with a cure for the disease in the game.
Mark was also deeply upset over the whole concept of Calm Time, in which he played a serial killer who was forced to kill everyone in the game. Including a young child and his teenage babysitter. Imagine the white phosphorous incident from Spec Ops: The Line and you'll understand why Mark got so upset.
Not only that, he played Calm Timeright after a session of DrunkMinecraft.
OFF already started to wear him when he learns that "purifying" a Zone leaves it drained of colour and life, but he really got creeped out by The Reveal in Zone 3 and by the Critic Burnt, so much so that instead of his normal outro he uses a negatively-colored clip of the Critic Burnt crying for help with no other sound.
It is then later topped by the "battle" against Hugo, which was received by a pure "No. Just... No" Reaction and repeatedly (and uselessly) pounding any option but the ones he was supposed to.
His reaction to 'The Markiplier Project' video. The video was a thank you from the fans for his work and dedication, all while congratulating him for 20,000 subscribers. What's really sad, but also a Heartwarming Moment is how touched he was by it. Seeing him crying in the beginning by how touched he was and his total loss of words is pretty sad, but touching.
His reaction to the Dreadhalls Oculus Rift game. He was so scared out of his mind he literally was in tears. The fact he was pretty much being angry throughout the video didn't help...
His playthrough of the Markiplier fangame Ripest of Fears starts out innocent (read: scary) enough. Then, Mark reaches the end and the game starts playing footage of his subscriber milestone V-logs. The revelation he has and the conclusion he comes to are a little heartbreaking, to say the least...
In Off, he finds Judge in the now purified Zone 2, meowing and mourning his brother's death. Mark is somewhat hammy about it, but still seems genuinely sorry and sad about what happened.
His 3,000,000 Subscriber Milestone video piles so much inspiration into a short time span that you'd be hard-pressed not to tear up. Mark himself is audibly holding back tears himself at several points.