use translation key for comment error

www/pad/comments.js

@@ -376,8 +376,7 @@ define([
                     return;
                 }
                 var author = typeof(msg.u) === "number" ?
-                                ((Env.comments.authors || {})[msg.u] || {}) :
+                    ((Env.comments.authors || {})[msg.u] || {}) : { name: msg.u };
-                                { name: msg.u };
                 var name = Util.fixHTML(author.name || Messages.anonymous);
                 var date = new Date(msg.t);
                 var avatar = h('span.cp-avatar');
@@ -786,7 +785,7 @@ define([
                 // Abort if our selection contains a comment
                 console.error("Can't add a comment here");
                 // XXX show error
-                UI.warn(Messages.error);
+                UI.warn(Messages.comments_error);
                 return;
             }