OK. I checked the following: in my Moodle 2 installation (where I want to give access for remote users coming from Moodle 1.9) I went to the page Setting > Site administration > Networking > Peers > my Moodle1.9 host > Profile fields. Here, in the list of "Fields to import" nothing was selected, instead the checkbox "Use the default settings instead" below the list was checked.
Unchecking this checkbox and selecting the "confirmed" field in the list results in the following: Now when a user coming from Moodle 1.9 for the first time to Moodle 2, a new user record is created in the Moodle 2 mdl_user table with the "confirmed" field set to 1 (before it was 0).
Is it this what you mean? If so, at least a hint in MoodleDocs should be given: I followed the instructions on http://docs.moodle.org/en/Moodle_Network#Peer_to_Peer_Network and here the information of importing/exporting user fields is missing.
By the way: As a Moodle admin I expect that "Moodle works fine with the default settings". So if the default in Moodle network configuration for imported/exported fields ist "use default settings" - do I have a chance to see that my users coming from remote are not confirmed and change this setting to "confirmed" somewhere in Moodle? Or in other words: If the default configuration leads to the fact that users "after a while will disappear", than it seems to be a bug or not? At least it is a lack of complete instructions on Howto setup Moodle network, isn't it?
To prevent missunderstanding: I dont want to critisize the programming, I just want to understand what the default settings in this case are good for 
Best regards,
Gisela