You should be able to localize messages for dynamically added methods. Currently, it is possible to add custom method messages to the messages object but calling addMethod stomps previous entries even if no message is passed.

I would like to be able to omit the message argument in the addMethod call and have any previously defined messages for that method survive. Today, they will be overwritten with undefined. The following change effects the desired behavior.

addMethod: function(name, method, message) {
...
$.validator.messages[name] = message || $.validator.messages[name];
...
}