Try covering up the names of these while guessing what each is supposed to symbolize. Personally, I found some of these to be rather unintuitive and sometimes arbitrary.
Would exclamation or question marks be intuitive if we'd never seen them before? Not that I think we should be adding more punctuation, but I don't know that we use '?' to question because it naturally looks like it's questioning something.
Interesting. I hadn't previously thought about the form of those punctuation marks.
Upon looking at them, a dot intuitively ends a sentence. A dot with a line intuitively ends a sentence with emphasis, and a dot with a meandering line questions.
From that perspective a question mark really does indicate uncertainty and possibly a question.
It's been in use for about a half century; it's typically described as “nonstandard”, though given the absence of a standards body for English it's not clear what that means.
It's definitely “real” in the sense of being in actual use in the wild with a clear and well-understood meaning.