What is interesting to me about commas is the examination of how they've been used over time. About a year ago here on AWAD I brought up a passage from an 18th-century writing that was so well-peppered with commas that it seemed to have about as many commas as words. I think it may have been Faldage who commented it was pretty typical of the period.

I tend to teeter-totter between the grammatical and rhetorical placement of commas and really don't mind too much how people use them unless the commas (or lack of) interfere with understanding or reading. Sometimes a comma will keep you from reading two words next to each other as directly related, when, in fact, one is the end of a phrase and the other is the beginning of a new phrase. Wish I had an example ready, but I don't. I also tend to be old-fashioned about certain comma rules and I assume I'm in a minority here--specifically, I do set off nonrestrictive clauses with commas and do not do so with restrictive clauses. I'm fairly careful about the use of 'that' and 'which,' and I realize that pinpoints me as having a foot in the old school. But, hey, it gives me a sense of being living history.