Yes, he has. Markiplier often does unique and entertaining segments, and this could be one of them. He likes to interact with different types of content related to his fan base, and reading fanfics, even the not - so - good ones, is a way to do that.
To add a filter to a story, start by deciding on the criteria for what you want to include or exclude. Then, you can apply this during the planning and writing process. It could be based on character traits, plot points, or the overall mood.
You can usually find the comic filter option in the settings of the app or software you're using. Just look for something like 'filters' or 'visual effects'.
Well, it depends on what you mean by 'real'. Technically, there are AI-based tools and algorithms that can be applied to manga to achieve filtering or manipulation effects. But their effectiveness and accuracy can vary.
I don't think it's a true story. Such heist scenarios are often the creation of writers and storytellers to provide thrilling and adventurous experiences. There's no evidence to suggest it's based on reality.