OK, this is reopened. It doesn't seem to matter whether the passwords are the same or different. If different, no error message is flashed. If same and the other fields entered correctly, the form doesn't seem to submit, the db isn't updated, and the page redirects right back to register again.
Again, if anyone has a working example of a custom submit MCV I would very much like to see the whole thing. From the number of threads discussing this problem, I suggest a working example be published in an easy to find location.