Hello guy!
JA Comment plugin allows integration of popular external commenting systems into the Joomla! articles. All users were managed by each comment service you choosed, Those users do not manage by joomla system, so that you have not any way to set permission on the commenting as you mentioned.
– But In the plugin’ setting, you can use the Access Level parameter which allow the plugin work with one or many user group you would like.
– Or you use other extensions instead of this plugin and I think you should wait for downlad the ja comment component, it’s preparing to replease 🙂