It looks like the form is just

<w:instrText>HYPERLINK "http://example.com"</w:instrText>

So this should be simple to support.

It's actually more complex than I thought. This whole contraption has to occur in a structure like this:

<w:r>
<w:fldChar w:fldCharType="begin"/>
</w:r>
<w:r>
<w:instrText xml:space="preserve"> DATE </w:instrText>
</w:r>
<w:r>
<w:fldChar w:fldCharType="separate"/>
</w:r>
<w:r>
<w:t>12/31/2005</w:t>
</w:r>
<w:r>
<w:fldChar w:fldCharType="end"/>
</w:r>

See http://officeopenxml.com/WPfields.php
Field types are documented here: http://officeopenxml.com/WPfieldInstructions.php

@jgm and @trapias -- just wanted to let you know that, a year later, I finally addressed this. Definitely not a good first issue -- accumulating runs in state, introducing a new module with its own little parsec parser. But there's now a framework for handing further fldChar/instrText directives in docx documents.

@jkr great, thank you! Will make a test ASAP 👊

Great -- if you do create a test document, can you post it? I'd prefer to replace the one that's up there now, but recent versions of Word don't seem to be able to produce links as fields.

@jkr for sure - cannot assure I can before 10/15 days, but finally will revert to you!