As I have stated on other occasions, there is widespread confusion or perhaps lack of understanding of what the terms “essential” and “nonessential” mean in punctuation.

I would say again: Putting a pair of commas around an element does not always mean that you can take it out of the sentence and have the sentence make sense. In other words, not all pairs of commas surround a “nonessential” element. You cannot always remove an element that is surrounded by commas and have the sentence make sense.

Consider:

…He lived in Springfield, Ohio, and not in Springfield, Illinois, during that period of time.
…She called on May 24, 2015, and not on May 24, 2016, with the news.

Removing the elements that are surrounded by commas in these setnences would leave the sentences without meaning. However, that does not mean that we take the commas out. The commas are there in each sentence because there is a rule that the state be surrounded by commas after the city and that the year be surrounded by commas after the full date.

Consider this scenario:

…I want you to have 40 percent, Mr. Roberts, and you to have 25 percent, Mr. Williams.

Again, if we remove the names because they are surrounded by commas and are therefore “nonessential,” the sentence loses clarity. We surround direct address with a pair of commas without regard to whether that name is vital to the meaning of the sentence or not.

In summary, not all pairs of commas are placed/not placed because of the concept of essential/nonessential. In fact, many pairs of commas are placed around elements that are absolutely necessary to the meaning of the sentence but have commas because there is a rule for those commas.

I hope this helps.

Happy punctuating!

Margie