What title do you hold after you've defended but before you graduate? Two friends successfully defended their dissertations yesterday, and many people have congratulated them, calling them Doctor so-and-so. I explained to my wife that they actually don't have that title until the graduation ceremony, that it's similar to a President-elect, who isn't called the President until they are sworn in. So, what title does a doctoral candidate take after they've defended but before they graduate?
There isn't a formal, universally accepted title here. The general standard has been to call them "Doctor" since everything else is in principle a formality.

The only other note that I'd make is that it's not commencement that makes the student in question a doctor, but rather conferral of the degree by the university. Some universities may confer degrees multiple times per year, but only have one commencement ceremony.

So, I would not include "Ph.D." next to my name, but in the education of my CV, I'd write "Ph.D. (to be conferred Month Year)," as that is entirely accurate representation of the state of affairs.