Why in file components/com_k2/helpers/permissions.php function getK2UserGroup use only K2 user tables? He should use both joomla and K2.By default the k2_users is empty. When I wont to write comment to article it is not possible because no permissions are loaded.thanksjoomla 1.5.20k2 2.3

If you have disabled joomla login, and enabled k2 login, a k2 user will be created when you registar.
all new users are assigened to a k2 user group
now if you log in all is well.