How important is the comma before "too".

Grammar books usually state that "too" is an additional word and should be set off by a comma when used at the end of a sentence.
  • He likes to play tennis, too.
I find people leaving it off even in formal writings. It makes me wonder, is it acceptable to leave it off, or should "too" always be set off by a comma in this context?

Thank you very much.
Most rules for commas are not hard and fast, with emphasis placed on clarity: is the comma necessary to convey the information clearly and accurately? Michael Swan (Practical English Usage) seldom uses a comma after a terminal too, nor do I if the sentence is short and sweet. It seems to me that here it depends somewhat on the man's other likes (as well as the context):

He likes to play golf, and tennis too. (= he likes to play golf-- and, oh yes, he also likes to play tennis.)
He likes to play golf and tennis, too. (= he likes, e.g., to tapdance-- and, oh yes, he also likes to play golf and tennis.)
He likes to play golf and tennis too. (= he likes to play baseball-- and, oh yes, he also likes to play golf and tennis.)

I may have gone too far in this, however.
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to comma or not, in my book, is chiefly a matter of intonation. see [url=http://www-personal.umich.edu/~jlawler/aue/commas.html ]John Lawler on comma use[/url]


'One man can't punctuate another man's manuscript any more than one
person can make the gestures for another person's speech.' - Twain
Thank you very much, Mister Micawber and Sam C, that really made sense. Next time when I see somethine like that, I'll try to look at the meaning of the sentence more in depth.
Hi. I would appreciate it if you could tell me if the three, pauses, intonation, and (what you brought out) clarity, are equally important considerations for comma use. I think I have a fairly good grasp of what it means to have "clarity" as a consideration in comma use, but I don't seem to have a firm grasp as to the other two, pauses and intonation. Could you give me some simple examples if you could? Or perhaps some illuminating words? Thank you in advance.
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