According to the current changes.xsd schema, the action element in changes.xml has text content only, ie no markup is allowed inside <action>. So I think the current behavior is actually correct. However, wrt to backward compatibility and functionality, this is not very satisfactory.
Note that in maven 1, the <action> element could contain arbitrary xdoc markup, for the announcement only the text content was extracted.
I think the proper solution would be to mimic this behavior, ie generalize the xsd schema and process the content of changes.xml according to where the output goes. A configuration parameter seems unnecessary to me, at least you would have to make it consistent with the xsd.