LC Comment: Rewriting by intermediaries

Section 3.1 of the core states that "These properties [i.e., MAPs] are 
immutable and not intended to be modified along a message path."  The 
SOAP binding amplifies this by saying first (in section 3.2) "When 
sending a message each property is represented using the appropriate 
element information item as a SOAP header block." (i.e., properties must 
be represented as header blocks), and (in section 6.1) "To avoid 
breaking signatures, intermediaries MUST NOT change the XML 
representation of WS-Addressing headers. Specifically, intermediaries 
MUST NOT remove XML content that explicitly indicates otherwise-implied 
content, and intermediaries MUST NOT insert XML content to make implied 
values explicit." (i.e., the header blocks must not be changed in transit).

However, the SOAP binding also says (in section 3.2), "Note that the 
message addressing properties gathered by an intermediary when receiving 
a SOAP message do not necessarily get replayed as MAPs when resending 
the message along the message path." and also (in section 2.2) that "A 
binding that supports this feature MUST provide a means to transmit the 
properties listed above with a message and to reconstitute their values 
on receipt of a message."  This last statement appears to imply that 
there are means other than simply putting the properties in the envelope 
as headers.

Several questions arise:

    * In what scenarios would " message addressing properties gathered
      by an intermediary ... not necessarily get replayed ..."?
    * Is a binding required to put MAPs on the wire as headers, or may
      it use transport-specific representations (e.g., any routing
      headers used by an underlying transport) without echoing them as
      SOAP headers?
    * Is an intermediary forbidden from changing headers in all
      circumstances, or only when those headers are signed?

The spec seems unclear, in that there are statements that at least 
appear to conflict.  Unfortunately, I can't propose a clarification 
without better knowing the intent.