That ship has sailed. This usage dates back to the time of Dickens, Brontë, Joyce, etc [1]:
As Dan Smith has pointed out in his reply to my comment on Mike Ruiz's answer, this usage crossed over into general acceptability quite a while ago, having been employed in works by Charles Dickens, Charlotte Brontë, William Makepeace Thackeray, James Joyce and Thomas Hardy, and so on. What might be happening is sort of a "resistance" against this meaning of literally, which people are starting to believe should mean something closer to what it originally did.
Sean Hou's answer in that Quora thread is the correct one. The word "literally" never means "figuratively" or "hyperbolically", but it can (like any other word) be used figuratively or hyperbolically. By analogy, someone can dishonestly say "Honestly, I didn't do it," when they did. This doesn't change the meaning of the word "honestly". There are no words in English that cannot be used in a lie, and neither are there any words that cannot be used in hyperbole or metaphor. You can, if you like, dislike hyperbole (I dislike dishonesty!) but there is no use worrying about the meaning of the word.
They are wrong. Native speakers just don't use definition 2 in a literal way. Maybe this usage will evolve (now that the dictionaries are wrong) but it doesn't explain any of the common usage.
> Native speakers just don't use definition 2 in a literal way.
Unclear if you meant some kind of irony by using "literal" here, but as a native English speaker I can assure you the second meaning ("used in an exaggerated way to emphasize a statement or description that is not literally true or possible") is frequently used.
This usage is indeed very common, but it is always meant and understood hyperbolically, and the meaning of the word relied on by the hyperbole is just M-W's sense 1.
To see this, remove the word "literally" from such a sentence. You are generally left with a statement that is still hyperbole or metaphor and not literally true. Which word are you going to redefine in a sentence like "It turned the world upside down." to enable you to interpret it literally? If you understand it as hyperbole, why does adding the word "literally" require any special meaning for that word?
Conversely, if you believe that the word "literally" literally can mean "not literally", in the same way that, say, "cleave" is an auto-antonym, it would authorize statements like
(*) When you use metaphor, you are speaking literally.
(*) What I said was the plain truth, but John took it literally.
which I think you will agree are not standard usage.
Moreover, if you replace the word "literally" in a sentence like
"It literally turned the world upside down."
with something that means "not literally", like
"It figuratively turned the world upside down."
it changes the meaning. The first sentence is hyperbole and the second is awkwardly literal.
I understand the desire of lexicographers to document this usage, which is as you say common (and legitimate) and seems to confuse people, but it's just not a different meaning of the word.
Interestingly, there is actually a long history of literally switching back and forth between its original meaning and "figuratively" over the ages. My fiance did his thesis on it!
As Dan Smith has pointed out in his reply to my comment on Mike Ruiz's answer, this usage crossed over into general acceptability quite a while ago, having been employed in works by Charles Dickens, Charlotte Brontë, William Makepeace Thackeray, James Joyce and Thomas Hardy, and so on. What might be happening is sort of a "resistance" against this meaning of literally, which people are starting to believe should mean something closer to what it originally did.
[1] https://www.quora.com/How-did-the-term-literally-come-to-mea...