Are you seriously suggesting there's a profound loss of meaning between:

> There’s a moment in your book that I love, when you give advice to awkward people looking for social shortcuts, and you tell them not to be literal wallflowers.

and

> There’s a moment in your book that I love, when you give advice to awkward people looking for social shortcuts, and you tell them not to be wallflowers.

Why does the threshold have to be "profound" for word choice and phrasing decisions?

There is a non-trivial difference in connotation between the two sentences.

In vernacular conversation "wallflower" can be used as a term to connote (strong) shyness or to indicate generalized presence on the periphery of an event. In the sentence from the article, "literal" helps to shift emphasis away from the "shy" connotation. Without it, or some other way to emphasize connotation, the sentence is easier to misinterpret as follows:

"..., and you tell them not to be too shy."

Yes. The former can be argued as more polite, because you're suggesting an alternate course of action (don't stand near wall), and the latter can be construed as an attack on a person's mentality (you're a shy person, don't be that way [that's bad]).

> The former can be argued as more polite, because you're suggesting an alternate course of action ...

alternative

In US English at least, alternate can be used as a direct synonym for alternative. Idk if it's the same in British English. Might be different like the phrase "just in case", etc.

Couldn't this whole thread be avoided if they had said, "and you tell them not to stand by walls". Or even, "not to literally stand by walls" - both work in this case! :-)