Over the last 10 years and counting, using less punctuation has slowly become a trend. Writers will eliminate the comma before too in sentences such as, “I attended the meeting too.” The Chicago Manual of Style says, “In most … cases, commas with this short adverb are unnecessary.”
Even nonrestrictive clauses are not always set off by commas any more if leaving them out does not confuse a reader. For example, “California was a province of Mexico from 1821 until 1848 when Mexico ceded it to the U.S.” Because “when Mexico ceded it to the U.S.” is a nonrestrictive (or nonessential) clause that adds extra information, it would typically be set off by a common before when.
Here’s what the GPO Style Manual, the style guide for the federal government, says about punctuation.
“Punctuation is used to clarify the meaning of written or printed language. Well-planned word order requires a minimum of punctuation. The trend toward less punctuation calls for skillful phrasing to avoid ambiguity and to ensure exact interpretation. The GPO Style Manual can offer only general rules of text treatment. A rigid design or pattern of punctuation cannot be laid down, except in broad terms. The adopted style, however, must be consistent and based on sentence structure.
The general principles governing the use of punctuation are: If it does not clarify the text it should be omitted; and, in the choice and placing of punctuation marks, the sole aim should be to bring out more clearly the author’s thought. Punctuation should aid reading and prevent misreading.”