WriteWorld: Punctuation: The Comma
Comma (n): A mark of punctuation used to indicate a division in a sentence, as in setting off a word, phrase, or clause, to separate items in a list, to mark off thousands in numerals, to separate types or levels of information in bibliographic and other data.
Consider the lowly comma.
If you regard it as a mere flyspeck with a tail, that may account for the some capricious uses (and non-uses) of it that appear from time to time.
