Comma w/ Participial Phrases?

Taken from the Grammar Girl:

 

Sometimes You Need a Comma With Participial Phrases, and Sometimes You Don’t

Today, we’re revisiting the concept of restrictive versus nonrestrictive elements. In past Grammar Girl episodes, I’ve talked about how to use the words “which” and “that” with restrictive and nonrestrictive elements. This time, we’ll help you figure out what the concepts of restrictive and nonrestrictive have to do with participial phrases such as “making me cry” and “banging his nose” and when to use a comma before such phrases.

What’s the Difference Between Restrictive and Nonrestrictive Clauses?

In case you’re not up on the concepts of restrictive and nonrestrictive clauses, here’s a quick review so we’re all on the same page. “A restrictive clause is just part of a sentence that you can't get rid of because it specifically restricts some other part of the sentence” (1). You could say, “The boy who threw up on Space Mountain wished he had stayed home.”  Here, the “who” clause is restrictive: It defines which particular boy wished he had stayed home, so you can’t delete the clause, nor do you use commas around it. 

On the other hand, “a nonrestrictive clause is something that can be left off without changing the meaning of the sentence. You can think of a nonrestrictive clause as simply additional information” (1). Such clauses “are usually surrounded by, or preceded by, commas” (1). An example is the “which” clause in this sentence: “The town, which lies thirty miles from the capital, is famous for its potato festival.” The “which” clause is surrounded by commas. It contains additional information that is not necessary to understand the sentence, so you can delete the clause if you want.

It can be easy to get confused about restrictive and nonrestrictive elements, so remember this: If it’s extra information, use extra commas.