I have no style

Which is really embarrassing considering how many English degrees I have.

So, I'm looking at the new Illustrated Elements of Style and I see this:

1. Form the possessive singular of nouns by adding 's. Follow this rule whatever the final consonant. Thus write,

Charles's friend, Burns's poems, the witch's malice.

Now, I always though that if the word ended with an 's' then you just placed an apostrophe after that and that was the possessive. But, Strunk and White say that is only the exception.

• Exceptions are the possessives of ancient proper names ending -es and -is, the possessive Jesus', and such forms as for consicence' sake, for righteousness' sake. But such forms as Moses' Laws, Isis' temple are commonly replaced by: the laws of Moses, or, the temple of Isis.

Hmmmm. Did you get all that? I didn't. Damn rules of grammar.....