Why is there no comma before "and" before this independent clause?

This was at a moment when the magistrate, overcome with tiredness, had gone down into the garden of his house and, dark, bent beneath some implacable thought, like Tarquin cutting the heads off the tallest poppies with his cane, M. de Villefort was knocking down the long, dying stems of the hollyhocks that rose on either side of the path like ghosts of those flowers that had been so brilliant in the seasons that had passed away.

Why is there no comma before the bolded and? My understanding is that there is an independent clause on each side of the bolded and.

By the way, the subject of the two independent clauses is the same.

Solution 1:

You are assuming a rule that I believe is a pseudo-rule (perhaps you could quote this 'rule' from some grammar?) I'd personally have no trouble with

Tom went to France and Dick went to Belgium.

It's clear enough. The addition of a comma before and would not worry me either - I'd add a pause if reading that version.

Here is an endorsement of the optional dropping of that prescriptive comma:

When a coordinating conjunction connects two independent clauses, it is often (but not always) accompanied by a comma:

Ulysses wants to play for UConn, but he has had trouble meeting the academic requirements.

When the two independent clauses connected by a coordinating conjunction are nicely balanced or brief, many writers will omit the comma:

Ulysses has a great jump shot but he isn't quick on his feet.

( http://grammar.ccc.commnet.edu/grammar/conjunctions.htm )

What disturbs me far more is the rambling and over-punctuated nature of the example sentence. Two at least are needed - the garden-path flavour of the original might even lead some to misconstrue it, being led to believe that ' the subject of the two independent clauses is the same'.