It's a little more fancy, as it supports syntax coloring:  I have to subclass
DataEditorSupport to override createEditorKit(), and have to provide my own
SaveCookie and Environment support because someone got too tricky putting the
default implementation into a package private class (SimpleES) which is only
accessible via a static factory method (and hence, no subclassing).  I copied
the way Coyote did it, where one cuts & pastes all of SimpleES into my own
subclass and added the single overridden method.

I'll post a question on nbdev as to why this method is failing, but doubt I'll
get a response because the editor team rarely does -- if no response, I'll
bother Mila directly.

You ought to be able to use DataEditorSupport.create without copying SimpleES.
There is no need to override createEditorKit. The *.rules file should have a
well-defined MIME type; if you have registered a kit for that MIME type with the
editor module, it will be used automatically.

http://platform.netbeans.org/tutorials/nbm-mfsyntax.html

There was a need to override createEditorKit if one wanted to extend the Java
editor's syntax rather than writing yet another one.  However, the last editor
changes to support the tutorial you reference broke syntax coloring in my
module, so I am back to square one.  I'll re-implement as the tutorial describes
and hope for the best.

All fixed -- eliminated need for SimpleES inclusion by using the Manifest syntax
tutorial.