On Tue, 5 Sep 2017 16:29:52 +0200 Hans Hagen <pragma@wxs.nl>   wrote:

> On 8/30/2017 9:45 AM, Christoph Reller wrote:
> > On Mon, Dec 28, 2015 at 3:45 PM Christoph Reller
> > <christoph.reller@gmail.com <mailto:christoph.reller@gmail.com
> >>   wrote:
> >
> > There seems to be a problem with the structure information added
> > when using \startmatrix:
> >
> > A fix would be very much appreciated.
>
> should be ok now
>

Thank you Hans for this fix!

There seems to be, however, still a minor issue with a more complete MWE:
\math{
  \startmatrix
    \NC A \NC B \NR
    \NC C \NC D \NR
  \stopmatrix}

The resulting structure tree is as follows:
<document>
'-<math>
  '-<mrow>
    '-<mtext>
      '-<mrow>
        |-<mrow>
        | '-<mtr>
        |   |-<mtd>
        |   | '-<math>
        |   |   '-<mrow>
        |   |     '-<mi>
        |   |       '-"A"
        |   '-<mtd>
        |     '-<math>
        |       '-<mrow>
        |         '-<mi>
        |           '-"B"
        |-<mrow>            (*)
        |-<mrow>
        | '-<mtr>
        |   |-<mtd>
        |   | '-<math>
        |   |   '-<mrow>
        |   |     '-<mi>
        |   |       '-"C"
        |   '-<mtd>
        |     '-<math>
        |       '-<mrow>
        |         '-<mi>
        |           '-"D"
        '-<mrow>            (*)

The elements marked with (*) are IMHO unnecessary. Do you agree?

Cheers
Christoph