>Has DMOZ played with the idea of having submitters register
Dunno if DMOZ has. I have. (You probably know that Zeal has something roughly equivalent to this.) I haven't figured out how to make it work for us.
Your biggest problem is emotional: you want to know things we can't tell you, and -- frankly -- that cannot possibly make any difference in deciding what you need to do. (If you have a business, you need to be promoting it regardless of what the ODP does. If you have an informational site, you need to be telling people about it.)
Our biggest problem is spam. Doorway/affiliate spammers really do need the information you're asking for. They want to know what spamming techniques are hardest to detect, what spamming techniques are ineffective, and the information you're asking for is exactly what they need in order to figure that out. For spammers, our actions really do make a difference, since nobody will ever promote their sites, or even go to them if they didn't obtrude themselves in front of the real content-providers. Their ONLY hope is to fool disinterested parties like the ODP or Google. And every time we speak to submitters, this question has to be uppermost in our mind: "If a spammer hears this, will it help him get past our review process?" Every time.
So if you feel you're treated like a spammer: you are, in some ways you really are. We have the ability to review 20-50% more legitimate sites than are submitted every day: it is spam, spam alone that causes all the delays you face, all the frustrations you feel, and all the reserve with which we receive all your communications. We have to ask of every single submittal "how could they be hiding spam under this one?" Only after your submittal has been reviewed and declared spam-free can we treat it as an honest submittal -- but by that time you've gotten what you wanted, and there's no reason for any more communication between you and us, ever!