Should there be commas before sentence-ending words such as 'too', 'either', 'apparently', 'obviously' and 'respectively'? [duplicate]

Should there be commas before sentence-ending words such as 'too', 'either',  'apparently', 'obviously' and 'respectively'?

• He wants to go to the mall, too.

• She's not attending the meeting, either.

• He is upset, apparently.

• She won't be going now, obviously.

• Mike and Bob scored 10 points and 14 points, respectively.

Is there a rule about whether to include or omit the commas?

See in the Chicago Manual of Style FAQ, which is publicly available:

Chicago Manual of Style

Commas

Q. Please help clarify a debate over what I see as a groundless but persistent carryover from high-school English classes: the comma-before-too “rule.” The rule goes something like this: When “too” is used in the sense of “also,” use a comma before and after “too” in the middle of a sentence and a comma before “too” at the end of a sentence. I am editing a work of fiction in which the author has rigidly applied the rule. I have just as rigidly deleted the commas. My managing editor believes that a comma is needed when “too” refers to an item in a list and has the sense of “in addition” (e.g., “I like apples and bananas, too.”), but she would omit the comma when “too” refers to the subject of the sentence (e.g., “Oh, you like apples and bananas? I like apples and bananas too.”). My managing editor’s rule helps make a useful distinction, but I am still wondering whether the comma is ever grammatically justified.

A. A comma can do some work in making the meaning of a sentence clear, but to claim two different meanings for I like apples and bananas too with and without a comma before too puts too much pressure on the comma. Out of context, neither version would be perfectly clear. To make the different meanings more apparent, short of additional context, you’d have to be more explicit:

I too like apples and bananas.

I like not only apples but bananas too.

Use commas with too only when you want to emphasize an abrupt change of thought:

He didn’t know at first what hit him, but then, too, he hadn’t ever walked in a field strewn with garden rakes.

In most other cases, commas with this short adverb are unnecessary (an exception being sentences that begin with too—in the sense of also—a construction some writers would avoid as being too awkward).

However, at COCA (CORPUS OF CONTEMPORARY AMERICAN ENGLISH), out of the total of

54602 instances of

TOO .

37350 have a comma

, TOO .

thus comma is much more prevalent "out there" than recommended by CMOS.

Personally, I'd say that whenever the writer wants to suggest a pause/break in speech before "too," in order to make it more emphatic, he/she should use a comma. In fiction, [that would be the case] esp when dealing with characters that prefer inflecsion in speech, or are more "theatral."

Punctuation, of course, is not a linguistic issue, but sometimes commas are used at the end of intonation phrases, and where intonational phrases end can be interesting. When "too" is a postmodifier of a noun phrase, it's part of the same intonation phrase as the noun phrase that it modifies, so you wouldn't expect to see a comma before it:

Louise eats [[NP sturgeon] too ].

means she eats sturgeon as well as eating other things. But

Louise [[VP eats sturgeon], too ].

means she eats sturgeon as well as engaging in other activities. And

[[S Louise eats sturgeon], too ].

means Louse eats sturgeon as well as other relevant things being true.