This is an amended fragment of jquery.validate.js (https://github.com/jzaefferer/jquery-validation). The change is to take the value returned from validator.settings.submitHandler.call, and return that value from the handle function. This means that a page that uses submitHandler to take some action upon a successful validation can simply return…

jquery.validate.submithandlerfix.js

// validate the form on submit
this.submit( function( event ) {
  if ( validator.settings.debug ) {
		// prevent form submit to be able to see console output
		event.preventDefault();
	}
	function handle() {
		var hidden;
		if ( validator.settings.submitHandler ) {
			if (validator.submitButton) {
				// insert a hidden input as a replacement for the missing submit button
				hidden = $("<input type='hidden'/>").attr("name", validator.submitButton.name).val(validator.submitButton.value).appendTo(validator.currentForm);
			}
			var doSubmit = validator.settings.submitHandler.call( validator, validator.currentForm, event );
			if (validator.submitButton) {
				// and clean up afterwards; thanks to no-block-scope, hidden can be referenced
				hidden.remove();
			}
			// Return the result of submitHandler instead of always returning false
			// Means that the presence of submitHandler does not have to block propagation of the submit event
			return doSubmit;
		}
		return true;
	}

	// prevent submit for invalid forms or custom submit handlers
	if ( validator.cancelSubmit ) {
		validator.cancelSubmit = false;
		return handle();
	}
	if ( validator.form() ) {
		if ( validator.pendingRequest ) {
			validator.formSubmitted = true;
			return false;
		}
		return handle();
	} else {
		validator.focusInvalid();
		return false;
	}
});