Learn English – What are the exceptions of using a comma in a simple sentence with a compound predicate joined by a coordinating conjunction

commas

The rule I learned is that a sentence with a single subject but a compound predicate that’s joined together with a coordinating conjunction must have no comma:

  1. I went to the lake but did not catch any fish.
    (one independent clause whose subject distributes across two verbs joined with a conjunction)

That rule states that a comma should be used only when two independent sentences are combined with a coordinating conjunction to create a compound sentence:

  1. I went to the lake, and I saw a duck.
    (two independent clauses, each with its own subject and verb)

However, I see this rule being broken time and again by popular writers where a complex sentence with a coordinating conjunction is separated by a comma. I take it that this rule, like so many other English “rules”, has room for exceptions.

So, in which cases can this “rule” be broken?

Edit:
I'm reading a book called "Known and Strange Things: Essays" by Teju Cole. In this book I saw a sentence that read "I'm not superstitious, and thought nothing of it." "Thought nothing of it" is a dependent sentence joined by a comma with the previous independent sentence.

Best Answer

“I'm not superstitious, and thought nothing of it” is no more a complex sentence than is “I went down to the café and ate“. There is no dependent clause here, nor is there a subordinating conjunction. There is a coordinating conjunction and a compound predicate. Those sentences are neither complex nor compound.

That said, it is unusual but not unheard of to use a comma before the conjunction in a compound predicate. This normally indicate a slight pause in speaking; a stronger pause might use a dash. It can also sometimes be used to disambiguate what might otherwise lead to a wrong parse in certain garden-path sentences.