BuddyPress.org

edit the theme file /activity/entry.php and under the activity-meta div – you’ll see the link for comments. you could add the following checks to that section:

bp_get_activity_object_name() == 'groups'  //the component name

groups_is_user_member( $bp->loggedin_user->id, bp_get_activity_item_id() )  //if a group then item_id references the group_id

(i didn’t test this – just what i found)