Round Tripping XML via low-end version?

The news that the custom schema feature will not be in the low-end version
of Word 2003 leads to one particular worry. Say I write a Word document that
includes custom tags, then I send the document to someone else to just edit
some of the text, not being sure what "version" of Word they have. If they
have Word-lite, will the custom tags disappear when the load or save the
document? Will the XML be lost by the time the document gets back to me?
This is a particular issue for publishers who send articles to external
authors for corrections.

Neil.