created comments with FactoryGirl

app/models/ability.rb

@@ -137,7 +137,9 @@ class Ability
     can :manage, Sponsor, conference_id: conf_ids_for_organizer
     can :manage, SponsorshipLevel, conference_id: conf_ids_for_organizer
     can :manage, Ticket, conference_id: conf_ids_for_organizer
-    can :manage, Comment, conference_id: conf_ids_for_organizer
+    can [:read, :create], Comment, commentable_type: 'Event',
+        commentable_id: Event.where(conference_id: conf_ids_for_organizer).pluck(:id)
+
   end
 
   def signed_in_with_cfp_role(user)
@@ -156,7 +158,8 @@ class Ability
     can :manage, CallForPaper, conference_id: conf_ids_for_cfp
     can :manage, Commercial, commercialable_type: 'Event',
                              commercialable_id: Event.where(conference_id: conf_ids_for_cfp).pluck(:id)
-    can :manage, Comment, conference_id: conf_ids_for_cfp
+    can [:read, :create], Comment, commentable_type: 'Event',
+                                   commentable_id: Event.where(conference_id: conf_ids_for_cfp).pluck(:id)
   end
 
   def signed_in_with_info_desk_role(user)

app/views/layouts/_navigation.html.haml

@@ -25,7 +25,7 @@
                 %b.caret
               %ul.dropdown-menu
                 = render 'layouts/user_menu'
-          - if can? :manage, Comment
+          - if can? :read, Comment
             %ul.nav.navbar-nav.navbar-right
               %li.dropdown
                 %a.dropdown-toggle{"data-toggle" => "dropdown", :href => "#", id: "unread-comments-preview"}