JBossUserGroupCallbackImpl in BPMS 6 does not allow the use of comma "," in Group Id

Issue

• BPMS 6 and jBPM6 overall allows the use of comma "," in Group Id, if used with the use of the org.jbpm.ht.user.separator system property. Where users need to specify the special character which would be used by jBPM6 task service for separating multiple group ids (other than the default character of ",") . However, if users are testing the same feature with JBossUserGroupCallbackImpl and where user's Group ID contains a comma "," , jBPM6 cannot process the User Task.
  e.g. User can set the properties for defining group ids for a user like this.

        ...
        properties.setProperty("john", "johngg");
        properties.setProperty("mary", "maryg,g");
        ...
        UserGroupCallback userGroupCallback = new JBossUserGroupCallbackImpl(properties);
        ...

Additionally, even if the user set the org.jbpm.ht.user.separator property to specify the group id separator , jBPM6 does not display the User Task (assigned to maryg,g Group Id) to mary who should be able to see/claim/complete the task.

        System.setProperty("org.jbpm.ht.user.separator", "#");

• Is this a bug? Is there a way to workaround it?