Confirmation-Mail after registration comes directly after mailadress is entered

I will flag your question for the developers. From what I understand, this option for creating the user on the add-listing page, is meant to be used for community sites where it is highly unlikely that users will come back to manage the listings. That said, the developers may have more ideas about this now that the feature is being widely used. As a best practice, though, if you want to have control over it, you should have the visitor register first before they view the add-listing page. That way you have control over the email through the user management plugin or through other WP facilities.