Why doesn't XPathDocument(validatingReader, XmlSpace.Default) preserve 
*all* the significant whitespace returned by the specified 
XmlValidatingReader (.NET Framework 1.1)? For example:

<!DOCTYPE p [
<!ELEMENT p (#PCDATA | b | i)*>
<!ELEMENT b (#PCDATA)>
<!ELEMENT i (#PCDATA)>
]>
<p>Here is <b>bold</b> <i>italic</i> text.</p>

The DTD says the <p> element contains mixed content, so when 
XmlValidatingReader reads this document, the XmlNodeType of the space 
between "</b>" and "<i>" is XmlNodeType.SignificantWhitespace. But the 
space is discarded by XPathDocument -- its private ReadChildNodes method 
treats significant whitespace as regular whitespace (which is then 
discarded) if the reader's XmlSpace property is anything but 
XmlSpace.Preserve.

Why does XPathDocument make this extra check for xml:space="preserve"?

(Since I don't want to put xml:space attributes all over the place in my 
documents, I'm going to pass XmlSpace.Preserve as the second argument to 
the XPathDocument constructor instead of XmlSpace.Default. But I'd still 
like to understand this behavior.)

Michael