I probably should have explained why I was doing this! I didn't mean
to imply that this filter would be good to enable for general browsing.
I'm not even going to use this in my normal configuration, but in a special
one that I will use for a very specific purpose.
I'm going to use it for non-browser, peer-to-peer web services,
where XML messages are being sent within SOAP envelopes
over HTTP. In this case, I wrote the SOAP sending and receiving code,
so I know exactly what is being sent and what filters I should or shouldn't
have enabled. I also cannot change the Content-type value, because
the receivers of the SOAP/XML messages explicitly check that value and
would reject anything like text/html.
Sorry I didn't explain myself more clearly. I was only trying to show the
concept of having to explicitly turn on filtering for Content types outside
the core set. I spent several frustrating hours trying to get filters to
apply to text/xml contents before concluding that it wasn't my filters
that were wrong, it was that no filters at all were being applied to text/xml
contents. Then it took quite a while before I finally found the hint that
I needed in the "Limitations" section of the Proxomitron help pages.