Ken:
Thanks for the well-thought-out reply!
I'm sorry; 2 has been out for so long I didn't think anyone was even using it anymore. I'm firmly in 2 land (in fact, both servers are at current stable—2.6.2). The administration of Moodle since it went to version 2 has been a non-stop headache, but in version one using Moodle was a non-stop headache, so I'll take it.
There's no need to move enrollments. I'm in Japan. We're in the break between academic years (for a couple more weeks at least!). If moving the enrollments will move the user profiles, then that's great. But that doesn't do anything for the vast majority of users who were not enrolled in classes in our department last semester. I have 1100 users, but I bet there are only maybe 100 or so active in a semester. If possible, I'd prefer not to require them to set up their profiles again because, being information studies majors, anything having to do with computer literacy to even a basic degree results in chaos (no, I don't understand either).
I'm actually really surprised this is so difficult. I'd expect an option that told Moodle that there is no password because the imported account is authenticated elsewhere.