CiviCRM Community Forums (archive)

Please check that this is not a behavior specific to Joomla, but perhaps it is true of all CMS.

Also the "edit groups" permission means quite literally to "edit groups in the Manage Groups page"  I don't think this permission applies to adding or removing contacts to groups, which is part of the "edit contacts" permission.

I do not know about 'adding new groups' but literally this is not editing, so perhaps adding is allowed under this 'edit groups' permission.

This may not be a bug, but a misunderstanding of what this permission is meant to do.  And admittedly the documentation about the permissions is not the best.  Perhaps if you feel like being a helpful member of the community you could volunteer to improve the documentation.