You never know.

migrations/071_banned_referrers.rb

@@ -0,0 +1,12 @@
+Sequel.migration do
+  up {
+    DB.create_table! :banned_referrers do
+      primary_key :id
+      String   :name
+    end
+  }
+
+  down {
+    DB.drop_table :banned_referrers
+  }
+end

migrations/072_banned_commenting.rb

@@ -0,0 +1,9 @@
+Sequel.migration do
+  up {
+    DB.add_column :sites, :commenting_banned, :boolean, default: false
+  }
+
+  down {
+    DB.drop_column :sites, :commenting_banned
+  }
+end

models/site.rb

@@ -496,6 +496,7 @@ class Site < Sequel::Model
 =end
 
   def commenting_allowed?
+    return false if owner.commenting_banned == true
     return true if owner.commenting_allowed
 
     if owner.supporter?