The usage of "let alone"

Question

Recently, my English tutor pointed out that I misused the phrase "let alone" in the following sentence:

Such high level of publicity of shame notions at different levels is very rare in other Asian countries, let alone in Western society.

By "let alone in Western society", I mean that Western society has even a lower level of publicity of shame notions than other Asian countries. While I was reviewing my document and reading other posts about the usage of "let alone", I don't believe that I understand this phrase thoroughly.

Could anyone help elaborate why "let alone" isn't correctly used in this sentence?

Do you think "let alone" is an informal phrase that should not appear in academic writings?

Clarification based on comments: I remember my teacher explained the usage of let alone in this sentence:

He bought her a diamond ring which was huge and sparkly, let alone expensive.

I didn't take detailed notes about this, which I regret, but it seems "let alone" means a greater extent of what is described in the first half of the sentence. For this same reason, I am now confused about it while reviewing my document a week after the discussion.

The context is shame is commonly mentioned in countries like China and Japan, but not so much in other Asian countries, whereas in the U.S., shame is extremely rarely disclosed or publicly discussed.

Answer 1

"Let alone" is an idiom, so it's usage is governed by more than its definition. It connects two things, one of which is a subset or requisite of the other. For instance, said of someone who just suffered a terrible injury, "He'll never walk again, let alone dance." Or, if you were terribly tired, you might say, "I don't think I can stay awake through the next commercial break, let alone for the rest of this program."

Because "Asian countries" is not a subset of "Western society," your use of the term misses the mark. Your tutor's example is closer. However, "let alone" is always used in conjunction with some kind of negation: don't, can't, won't, etc. "I don't have the patience to care for a puppy, let alone a baby." Or, "I wouldn't be interested in being your boyfriend, let alone your husband."

Answer 2

I think there's too much business in the specification to make good use of let alone. When one gets to the let alone focus, one has to go back and reparse "level of publicity of shame notions at different levels" to figure out what it is, and whether one believes it's higher or lower in N. America. That wastes the benefit of the construction.

You can probly get more ideas from this paper by Fillmore, Kay, and O'Connor, "Regularity and Idiomaticity in Grammatical Constructions: The Case of Let Alone", Language, Vol 64, No 3 (1988:501-38).