Please read http://moodle.org/mod/forum/discuss.php?d=106252 and http://moodle.org/mod/forum/discuss.php?d=104358
FULL STEPS TO REPRODUCE
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1. go to server A
2. backup a course together with user accounts
3. go to server B and log in as a Teacher or Course creator
4. restore the backup
WHAT WAS EXPECTED
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As neither Teacher nor Course creator have granted capability "moodle/user:create", no users are restored
WHAT ACTUALLY HAPPENS
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New users are registered. The Admin does not know anything.