Can "en" replace a words that start with "que" instead of "de"?

Question

(Note: This question essentially re-asks a question that is many years old, that already has an accepted answer. I figure it is better to re-ask the question, outlining why I don't understand the answer)

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In the textbooks that I've read, the pronoun "en" usually replaces a string of words, where the first word is "de" (or is the partitive article du/de la/des).

(The textbooks seem to say that the only exception is sentences that uses numerals like "trois" instead of "de", like "J'ai trois stylos" -> "J'en ai trois").

I've also recently asked a question, where I learned that sometimes "en" seems to be replacing words that start with "de", but that these words are implied in ways that might not be obvious for a beginner language learner. For example, if someone says "J'en ai la larme à l'œil", this can be thought to stand for "J'ai la larme à l'œil de voir ça".

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With this knowledge, I still cannot make sense of something written in the accepted answer in this French.SE question.

The question was asking about what the "en" stands for in this sentence:

Un jour, elle lui offrit un petit bonnet de velours rouge, qui lui allait si bien qu'elle ne voulut plus en porter d'autre.

The answer writes (the bolding is added by me):

"En" is a pronoun and its use is essential to the meaning of the sentence.

If we chose not to use "en", the sentence would read as:

"Un jour, elle lui offrit un petit bonnet de velours rouge, qui lui allait si bien qu'elle ne voulut plus porter d'autre bonnet que celui-ci".

If we omit "en" altogether, the sentence is incomplete and does not make sense:

"Un jour, elle lui offrit un petit bonnet de velours rouge, qui lui allait si bien qu'elle ne voulut plus porter d'autre".

The person who wrote the question accepted the answer, and seems to understand the answer. But I don't understand the answer! It seems that the "en" is replacing "que celui-ci", which confuses me.

Questions:

1. I'm confused about that "en" is replacing "que celui-ci". Is it really replacing "que celui-ci"?
2. The answer says that without the "en", the sentence is incomplete and doesn't make sense. (ie it is saying that ".... elle ne voulut plus porter d'autre" doesn't make sense). But it seems to make sense to me. Why is the sentence incomplete and not make sense?

Answer 1

En refers to the whole expression autre bonnet (que celui-ci), not just que celui-ci.

Without en, the phrase becomes:

elle ne voulut plus porter d'autre.

This indeed is incomplete because there is no indication about what autre is referring to. Maybe does "She no longer wanted to wear some other" work in English but in French, we need to tell some other "what".

Without d'autre but with en, the sentence is grammatical:

elle ne voulut plus en porter.

but its meaning is different. She no longer wants to wear any bonnet at all.

Answer 2

Upon re-reading a part of the book "The Structure of Modern Standard French" by Maj-Britt Mosegaard Hansen, I realize that I grossly misunderstood the use of en. It is far too simplistic to say that en usually replaces "de + _____".

The following excerpt applies to my question (but there are other uses of en discussed in the book) :

In addition, en is frequently used to represent only the head noun of an indefinite noun phrase, leaving both the determiner and any modifiers behind, as shown in (30)-(31) below. This is possible no matter what kind of indefinite determiner is used:

(30) Un train peut en cacher un autre. ( = Un train peut cacher [un autre train.]) (31) A: Je pourrais te piquer une cigarette, s'il te plaît ? B: Oui, mais je n'en ai que des légères. ( = Oui, mais je n'ai que [des cigarettes légères.]). (from Section 17.2.2 in "The Structure of Modern Standard French")

It is worth reminding myself that some indefinite determiners are:

• Indefinite Article
• Partitive Article
• Numerals

(from Section 12.1, "Definite and Indefinite Determiners")

Given the above information, how en is used in the sentences below now makes sense. The only thing I still must do, is to make sure I understand why "d'autre bonnet que celui-ci" and "des jolies perles" are considered indefinite noun phrases.

• Elle ne voulut plus porter d'autre [bonnet que celui-ci]
  Elle ne voulut plus en porter d'autre

• Elle portait des [jolies perles] roses.
  Elle en portait des roses.