See CMS 9.55 for usage of comma in numbers of a thousand and above, including index amounts—except in page numbers, years, and formal index titles.
Examples: The DJIA reached 4,000 long before 2002. The Wilshire 2000 includes more small companies than the S&P 500. The answer is found on page 1023.
If a word or phrase that would normally be set off by commas immediately follows a comma separating a compound sentence, use only the final comma.
Example: Liz went to town, and unless I am mistaken, she stayed all night.
(Not . . . “and, unless I am mistaken,” . . .)
Commas should be used to set off “Sr.” and “Jr.” (but not III as in Robert H. Smith III).
Example: Fred H. Speece, Jr., served as chair of the Board of Governors. Daniel J. Forrestal III also served as chair of the Board of Governors.