Sometimes

You could remove the comma in that sentence. The comma is always there, however, when rephrasing a noun or adding information that is non-essential.

More examples:

1. Anne, his sister, was not feeling well.
2. Anne, who jumps often, jumped too much, and her feet hurt now.
3. Anne won the Presidential election, requiring only a majority vote.

Excerpt from GrammarBook:

Rule 11. Use commas to set off nonessential words, clauses, and phrases (see the "Who, That, Which" section in Chapter One, Rule 2b).

 

Nonessential words, clauses, and phrases that occur midsentence must be enclosed by commas. The closing comma is called an appositive comma. Many writers forget to add this important comma.

The Purdue OWL also has a page on appositive commas that emphasizes the difference between essential and non-essential information and the requirement of commas. Excerpt:

In some cases, the noun being explained is too general without the appositive; the information is essential to the meaning of the sentence. When this is the case, do not place commas around the appositive; just leave it alone. If the sentence would be clear and complete without the appositive, then commas are necessary; place one before and one after the appositive.

Sometimes

You could remove the comma in that sentence. The comma is always there, however, when rephrasing a noun or adding information that is non-essential.

More examples:

1. Anne, his sister, was not feeling well.
2. Anne, who jumps often, jumped too much, and her feet hurt now.
3. Anne won the Presidential election, requiring only a majority vote.

Excerpt from GrammarBook:

Rule 11. Use commas to set off nonessential words, clauses, and phrases (see the "Who, That, Which" section in Chapter One, Rule 2b).

Nonessential words, clauses, and phrases that occur midsentence must be enclosed by commas. The closing comma is called an appositive comma. Many writers forget to add this important comma.

The Purdue OWL also has a page on appositive commas that emphasizes the difference between essential and non-essential information and the requirement of commas. Excerpt:

In some cases, the noun being explained is too general without the appositive; the information is essential to the meaning of the sentence. When this is the case, do not place commas around the appositive; just leave it alone. If the sentence would be clear and complete without the appositive, then commas are necessary; place one before and one after the appositive.

No

You would never remove the comma in that sentence. The comma is always there when rephrasing a noun or adding information.

More examples:

1. Anne, his sister, was not feeling well.
2. Anne, who jumps often, jumped too much, and her feet hurt now.
3. Anne won the Presidential election, requiring only a majority vote.

Sometimes

You could remove the comma in that sentence. The comma is always there, however, when rephrasing a noun or adding information that is non-essential.

More examples:

1. Anne, his sister, was not feeling well.
2. Anne, who jumps often, jumped too much, and her feet hurt now.
3. Anne won the Presidential election, requiring only a majority vote.

Excerpt from GrammarBook:

Rule 11. Use commas to set off nonessential words, clauses, and phrases (see the "Who, That, Which" section in Chapter One, Rule 2b).

Nonessential words, clauses, and phrases that occur midsentence must be enclosed by commas. The closing comma is called an appositive comma. Many writers forget to add this important comma.

The Purdue OWL also has a page on appositive commas that emphasizes the difference between essential and non-essential information and the requirement of commas. Excerpt:

In some cases, the noun being explained is too general without the appositive; the information is essential to the meaning of the sentence. When this is the case, do not place commas around the appositive; just leave it alone. If the sentence would be clear and complete without the appositive, then commas are necessary; place one before and one after the appositive.