When I type a question mark, it does not mean that I have a question, it means I think you have some kind of problem.
This is specifically referring to the common practice of typing a question mark as response on Chinese websites. It was a danmaku related practice first, but soon gained popularity in all forms of commenting and even memetic status.
Simply put, a single question mark means the commenter is seriously confused about the current situation. The commenter may have tons of questions, but the sheer confusion has overcome him, and all he can muster (or more accurately, type) is a single question mark. Some commenters may emphasize the slow process of typing this question mark by commenting with sentences such as "I slowly and doubtfully typed a ?." Like the text stated, the important part is not expressing one's confusion, but subtly expressing one's bitterness against the one causing the confusion, as if saying "what the fuck is wrong with you?"
Use this on anything that seriously defies logic. Those nonsensical life pro-tip videos everywhere are one of the best places for this practice.
e.g. In a life pro-tip video
Video: Mixing glycerin enema and vinegar creates a powerful solution that can help soften and whiten skin, keep using for a period of time for beautiful baby skin!
Commenter: ?