How do I understand l' and le in these subordinate comparison clauses?

Question

These are two example sentences in the grammar text I'm reading [1] :

(91) Stéphane est aussi grand [que l’est Benoît.]
(92) Il parle [comme le ferait un fou.]

I cannot understand these sentences because of the bolded l' and le.

My first strategy is to try and understand each [] bracketed clause.

1. That is, I don't know what "l'est Benoît" even means. Is l' some weird subject pronoun? (But since when could le be a subject pronoun?!) Is there instead an inversion, so really it is "Benoît l'est"; but even then, what is the l' replacing?!

2. Similarly, what is "le ferait un fou"? Is "le" the subject, and "un fou" the direct object? If so, what is "le" replacing?

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[1] ("The structure of Modern Standard French, by Mosegaard Hansen")

Answer 1

For the first sentence [que l'est Benoît.] :

• The meaning is the following: "Stephane is as tall as Benoît is.".
• Based on that, [l'est Benoît] means "Benoît is".
• Then, [l'est] is composed of a personal pronoun "le" elided and of the conjugated form "es(t)", auxiliary être in the 1st or 2nd person of the present indicative.

For the second sentence [comme le ferait un fou.] :

• The meaning is the following: "He speaks like a madman would do.".
• Based on that, the subject is "un fou" and le is attribute of the subject un fou

To represent a name determined by the definite article (le, la, les), by the possessive (mon…) or by the demonstrative (ce…), grammars recommend the use of the variable pronoun le, la, les and not not the neutral pronoun.

sources:

• Les attributs
• Sujets + verbes
• Inversion sujet + verbe
• COD
• COD
• COD
• Attribut Wiki

EDIT 1:

1. le does not "replace" anything in the English conversion of the french sentence; it's a reminder of grand indeed and it's attribute of the subject Stephane. This is not unusual to use le in that way, it's just one of the grammatical ways of writing a sentence in French.

Elle est aujourd'hui infirmière, mais elle ne l'a pas toujours été.

• l' means infirmière and it's attribute of the subject elle.

EDIT 2:

For the second sentence, le is direct object because it answers to the question "Who ?". Who's talking like a madman ? It is the subject: Il.

COD pronouns replace a person, animal, or thing name. This name or nominal group has the function of direct object complement or COD. It answers the question "who?" "For a person or an animal, and" what? For one thing.

Here's some example you can find in linked sources:

Il pense que demain il fera beau ? Oui, il le pense.

Tu écoutes le professeur ? Oui, je l’écoute.

Il parle comme le ferait un fou.

Answer 2

Non locuteur natif. Le/L' c'est ici ledit le impersonnel (ou pronom neutre). Voici quelques autres exemples :

Ce que vous avez cru facile ne l' est pas. (Balzac)

À cette époque j'en étais le propriétaire. Je ne le suis plus.

Le pronom est indispensable car être est transitif et exige (à peu près toujours) un complément d'objet.

Cf.

Tu ne les avais pas, je (le) sais.

Savoir peut être employé intransitivement et le pronom est donc optionnel.

Cf.

Lors donc que tu fais l’aumône, ne sonne pas de la trompette devant toi, comme font les hypocrites dans les synagogues et dans les rues, afin d’être glorifiés par les hommes. (Segond 1910, Mathieu 6.2)

Donc, lorsque tu fais un don à quelqu’un, ne sonne pas de la trompette devant toi, comme le font les hypocrites dans les synagogues et dans les rues afin de recevoir la gloire qui vient des hommes. (Segond 21, L'original avec les mots d'aujourd'hui, Ibid.)

Les deux formes sont possibles et équivalentes mais la tendance est à l'utilisation du pronom le. Son absence est aujourd'hui plus littéraire et très rare en français parlé.

[Voir les réponses de user @jlliagre aux questions ci-dessous :

Emploi dudit "le" impersonal (prénom neutre le)

Le pronom neutre « le » est-il facultatif ? ]

Answer 3

As it was explained in this answer the antecedent is not always nicely formulated in the linguistic context or indeed, sometimes, not at all. There is nothing new in those two examples, except the particular formulation they entail.

1/ Stéphane est aussi grand que (grand comme Benoit) est Benoit.

Here the antecedent has to be formulated by much extrapolation and the result is really a truism ("Benoit est grand comme Benoit".).

2/ Il parle comme le ferait un fou.

The antecedent which has to be extrapolated here too is rather simple to make out, and is according to the model provided in the answer referred to above.

• Il parle comme (l'action de parler) ferait un fou.

This gives us, taking into account the normal place of the "cod" according as it is a pronoun or not, "Il parle comme un fou ferait l'action de parler.".