ambivalent comment

I used to teach grammar but I know nothing. I pity my former students. But my girlfriend, who also used to teach grammar and is now an editor so should know these things, says that it just depends on what style you're following. Chicago style uses the 's (e.g., Charles's) except for a few exceptions like Jesus (which would only have the apostrophe); however, AP style just uses the apostrophe (Charles') for basically all proper nouns. For regular nouns both styles use apostrophe-only (the houses' front yards). The same is true for the comma question. One style book will tell you to do the string commas or whatever they're called, another won't. Safire (and others much more knowledgeable) was right that grammar is defined by usage, rather than the other way around. That means grammar is controlled by the 800-lb gorilla -- whomever is going to judge your writing will determine what is right, so your best bet is to learn what that person likes and stick with it. Comfortingly unceertain, isn't it?