We have to create this object that extends WMLVersion1_4Configuration in order to add the hr element to the 'always empty' list of elements.
A better approach (using delegation rather than inheritance) would involve providing an add method for the alwaysEmptyElements Set in ProtocolConfiguration. However, given the fact that configuration objects have previously been created as singletons, this will not work (adding an element to the WML1.3 static object's configuration will persist for the lifetime of that session).