"ABD" is just silly, IMO, and I'd avoid using it like the plague. To me, it carries nothing but negative connotation.
First, defending a dissertation is too big to be an "all but". It's the culmination of a serious academic experience. I've seen plenty of students get to that point only to have the degree disappear.
Next, the dissertation and the defense is a big step. Not being able to get your act together to write and defend when you're at the "all but" stage is a sign to academics that something is not quite right.
Finally, even if everything is going perfectly, and you've completed the research and writing it up will take the normal amount of time, then using an artificial title makes it look like you're anxious to have a title.
Long story short, when you start, use "Ph.D. student". When you've been advanced to candidacy, use "Ph.D. candidate", because that's what you are. I'll stick my neck out and say that when you've successfully defended and dealt with any corrections and revisions your committee wants handled, but you're just waiting for a ceremony, it might be OK to use Ph.D., but I'd leave it out, and on my CV I'd list Ph.D., with the date defended and the date the degree will be conferred.
In the USA, PhD ABD is ludicrous only to the arrogant academic. PhD ABD gives very important information to non-academic employers. Namely, it signals rigorous training in the production of knowledge process, as attested by passing qualifying exams necessary for Candidacy. By definition Candidacy attests one has the tools to endeavor in that process; i.e., dissertation project. A Master's degrees' objective is different: it is training in specialized analysis. A distinction in title to reflect the distinction in training is therefore appropriate.
PhD ABD also signals that one has chosen to work in the productive sector v. in Academia. Plenty of reasons to make that choice!
Whether someone left the PhD program due to their inability to complete the dissertation/coursework successfully or their free choice is very easy to tease out (e.g., in an interview process, via transcripts showing performance, etc.).
So to the orthodox I say: be more open-minded. Show nuanced discernment. Note that your fundamentalism is against Academia's core mission!
In the end, a PhD ABD who knew he/she was in the wrong place and cut their losses is much better off (economically, and arguably socially and psychologically) than a 7-year frustrated post-doc that can sign PhD after their name! Due to structural problems in higher-ed that is where most PhDs land. The people vilifying the PhD ABD in pejorative terms here and elsewhere sound like the latter trying to prove that although they are unhappy, at least "they did not fail" like the PhD ABD.
As a PhD ABD I can attest that could not be further than the truth! I am much happier with my lot! One, by the way, which most people call remarkably successful!
Yours truly, M.M., PhD ABD