There was little useful response to the issue of changes in <rendition> on the TEI list, so I'm going to have to make an executive decision to change the header encoding myself. This is what I think should be used:

<rendition xml:id="Transcription">
  <label>Transcription de texte</label>
  <code lang="text/css" rend="ellipse">color: #ff0000</code>
</rendition> 

Since I've already converted some files to an intermediate format, I've worked out a strategy for making the change:

1. Change the app so it writes out the new code format.
2. Load and re-save all of the files which have been changed so far (all three files in the tutorial folder are candidates, and some in test_data).
3. Rewrite the app loading code to read the new format.
4. Test file loading with the files previously saved as 1.6.
5. Update the conversion XSLT files to add the new rendition change.
6. Load a variety of known-good 1.5 files to check they load correctly, then save and reload them to ensure the 1.6 round-tripping is good.
7. Update the docbook conversion files so that they also use the new system, and test round-tripping some files to and from docbook.

Once docbook i/o is working, we need to start testing the help building system, which is based on mdh_docbook_to_html.xsl in the mdhHelp folder. Changes should not be required, but it should be tested.