Subordinate conjunctions optional use of comma— rules

Question

I noticed this usage on a website of parenthethesis around a subordinate part of the sentence: is this accurate use. Rather than talk about his chocolates (which are great by the way, if you’re in Leicester you have to go!).

and

Sarah, noticing that the weather was changing, went back for her coat.

So the above sentence has a subordinate clause in the middle started with ''noticing'', but what is difference between splitting that with parenthesis or m-dash. Are there rules surrounding how you separate a subordinate clause

e.g

The man who is coaching my team is my father.

The man, who is coaching my team, is my father.

Is the comma use around the subordinate clause optional or are there instances where it's mandatory.

Answer 1

Use commas around a "nonessential" subordinate clause. In the first example, "noticing that the weather was changing" adds some information about Sarah's environment, but it isn't essential to the meaning; we still understand "Sarah went back for her coat." (This type of subordinate clause is called an "appositive.")

The other example is not so easy, and in fact, it can go either way. Without commas, "who is coaching my team" is essential information, without which we would not be able to identify the father. There could be multiple men present, and saying "the man who is coaching my team" is a key identifying factor. With commas, however, "who is coaching my team" becomes nothing more than an afterthought. We already know who the man is, we're just providing a bit more information. The sentence still carries the same meaning without it - "the man is my father."

The key here is meaning. If the meaning of the sentence is dependent on the subordinate clause, do not use commas. If the subordinate clause is not essential, but only provides additional information or clarification, use commas.