Hi, What is bothering you? It clearly stated in the source you quote :
When a MESSAGE contains a soap:Fault element, that element MUST NOT have element children other than faultcode, faultstring, faultactor and detail.
INCORRECT:
It is incorrect becau, the DIRECT child of the <SOAP:Fault> may be :faultcode, faultstring, faultactor and detail. In this example as a direct child of <SOAP:Fault> element is also :
In the correct example:
the element
is NOT the direct child of <SOAP:Fault> element, but but child of <detail> element, within what it CAN have a declared a new namespace and the elements mapped to that namespace. So , however, it DOES NOT brake a rule, about what element must be a child of <SOAP:Fault> element. <m:Exception> element is a GRANDCHILD of <SOAP:Fault>.
Do you understand now?