I reported this internally just before the LC draft was published; I'm repeating
it as a public comment for the purposes of issue tracking.

See the URL referenced.

Consider the following code, executed with a document node as the context node.

<a>
 <xsl:copy>
  <xsl:attribute name="x">5</xsl:attribute>
 </xsl:copy>
</a>

In 1.0, the xsl:copy does nothing other than to cause the xsl:attribute
instruction to be executed, so the result is <a x="5"/>

In 2.0, the xsl:copy causes a shallow copy of the document node to be made; the
xsl:attribute instruction then fails because you can't add an attribute node to
a document node.

My view is that we can live with this incompatibility, but we should document it.

Michael Kay