Xjyuk

Он отправился в море, и наловил там много рыбы.

The above sentence is from my essay, and my teacher marked the comma as a punctuation mistake of mine. I strongly disagree with him. Being unable to persuade him that I am right, I decided to humbly ask native speakers on this SE. Please kindly resolve our argument.

I put this comma in order to convert a simple sentence to a complex sentence with two independent clauses, the second one having zero subject. I knew that the sentence would be perfectly okay without the comma, but I wanted to make a pause in this sentence. I wanted the reader to first imagine the setting off for fishing, then make a pause, and then imagine the fishing itself. Without the comma the sentence would read very quickly and be a single idea. I even considered putting a full stop instead of the comma.

At any rate, I believe that putting this comma is not against the Russian grammar rules. I believe I have the right to convert a simple sentence to a complex sentence by putting a comma. I believe that an independent clause with zero subject is still a valid independent clause. I believe that the phrase "и наловил там много рыбы" would even make a valid isolated sentence.

However, my teacher insists that putting this comma is a mistake. He says that a sentence with one subject and two verbs separated by the conjunction и must always be written without a comma.

I explained him why I had put this comma, and he laughed and said that only great Russian writers have the privilege of putting commas for reasons like this. He says that if I were Pushkin, he would consider my comma as a punctuation sign with its own deep meaning. He went as far as saying that my comma is a mistake because I am just a student. But I strongly believe that whether a comma is a mistake cannot depend on the author.

My question is this: Who is wrong - I or the teacher? In other words, is it a mistake to put this comma?

It is a simple sentence with two homogeneous predicates. There's only one subject both predicates refer to. That's why your teacher is right, there should be no comma in this sentence.

It is a common mistake nowadays when people are non-educated enough to put commas whenever they take breath. Even breaking the punctuation rules and common sense. That's why it sooner irritates than makes us pause.

I just want to add to the previous answer that putting a comma doesn't convert a simple sentence to a complex sentence. There is no such a rule and your teacher was totally right telling you that it's only writers' privilege to make one more simple sentence out of nothing, just by putting a comma.

A comma doesn't create any more main clauses than there are in the sentence. But if you don't put a comma you just make a mistake: you can't see the right ammount of grammar structures - main clauses.

I advice you to identify or underline all the main clauses in the sentence while you study. This is extremely useful. And after all remember that russian native speakers make really a lot of mistakes putting commas and mostly we take it easy. We really like to put commas where we feel to :)