with comma or without comma

[Yoshio]

Hello,

I have a question about participle.

Do we need a comma before participles (written in bold) in the sentences below?

She went out of the room singing merrily.
He sat on the rocking chair reading a book.

I have seen sentences both with and without commas. Do you have any stirct rules about comma or any differences in meaning?

I appreciate your help.

[David L.]

Use commas to set off phrases at the end of the sentence that refer back to the beginning or middle of the sentence.

So

She went out of the room, singing merrily.
He sat on the rocking chair, reading a book.

singing/reading refer back to she/he, not 'room' and 'chair', so set them off with a comma.

compare: He sat down on the woman reading a book.
Yes - right in her lap, squashing her book!

[Yoshio]

Thank you very much, David.

I wonder if you would answer another question.
My American friend says either would be fine, with or without a comma.
Are there possibly any differneces between BrE and AmE?
Or is it about formality? Or do you definitely use a comma in the sentences I wrote?

I appreciate your help.

[David L.]

In a sentence such as "He sat on the rocking chair reading a book', we do not say aloud '...chair, comma, reading a book' yet we understand what is meant - that it is the man who is both sitting and reading.
My American friend says either would be fine, with or without a comma.
The point is: because we can understand what is meant, does not make it correct and 'fine', particularly in written form. And as I thought I had shown :in the sentence -
He sat down on the woman reading a book
and
He sat down on the woman, reading a book

the comma gives it two completely different meanings.

Tis better to know the correct way and why - to avoid such anomalies - so you know when you can disregard the rule!
Language is to be played with. The more you are master of the language, the more you can have fun with it. Otherwise, it's the difference between someone who plays the piano, and someone stuck playing two-fingered Chopsticks.

[Yoshio]

Thank you very much, David.

Now I suppose I understand what you mean.
When and where to put a comma is very difficult for me to tell. We Japanese do have a similar punctuation as a comma, but it rarely makes big differences in meaning as in your example. We don't have any strict rules about the use of a comma, either.

Thank you again for your explanation. I really appreciate it.

[AntieAnnie]

In a sentence such as "He sat on the rocking chair reading a book', we do not say aloud '...chair, comma, reading a book' yet we understand what is meant - that it is the man who is both sitting and reading.
My American friend says either would be fine, with or without a comma.
The point is: because we can understand what is meant, does not make it correct and 'fine', particularly in written form. And as I thought I had shown :in the sentence -
He sat down on the woman reading a book
and
He sat down on the woman, reading a book

the comma gives it two completely different meanings.

Tis better to know the correct way and why - to avoid such anomalies - so you know when you can disregard the rule!
Language is to be played with. The more you are master of the language, the more you can have fun with it. Otherwise, it's the difference between someone who plays the piano, and someone stuck playing two-fingered Chopsticks.

Hi there... here's my American, non-teacher interpretation.

Without the comma, it would seem like the room was singing merrily:

She went out of the room singing merrily.

To be honest, if I were writing it, I would write it as follows:

Singing merrily, she went out of the room. I'm not sure if it's incorrect to start a sentence with the gerund form of the verb, but it seems to help me to separate the idea that she was singing merrily...

[Yoshio]

Thank you very much, AntieAnnie.

This kind of thing(the use of comma) is really difficult for me to tell, because my language Japanese is totally different from English.

Thank you for your help. It was really lucky for me to get replies from people from England, and America.