It would be boring if all the style manuals agreed. They don't. What most publishers settle on is a house style, which offers consistency of usage. One of my employers used a house manual to lay down rules such as which type would be used for various purposes.

Authors don't always like the house style: their instructions should then be followed (eg e e cummings).

I didn't like the open punctuation developed by the Civil Service: I now prefer the uncluttered appearance it gives to the page.

Stu