The Math-extension sadly doesn't support the phantom tag and shows an parser error:

Failed to parse (unknown function "\phantom"): {\displaystyle \frac{x+y+z}{x \phantom{+}\phantom{y}+z}}

Example code for mediawiki / TeX:

<math>\frac{x+y+z}{x \phantom{+}\phantom{y}+z}</math>

MathML code:

<math xmlns = "http://www.w3.org/1998/Math/MathML"> <mfrac> <mrow> <mi> x </mi> <mo> + </mo> <mi> y </mi> <mo> + </mo> <mi> z </mi> </mrow> <mrow> <mi> x </mi> <mphantom> <mo> + </mo> </mphantom> <mphantom> <mi> y </mi> </mphantom> <mo> + </mo> <mi> z </mi> </mrow> </mfrac> </math>

and here an example edit:

https://en.wikipedia.org/w/index.php?title=Wikipedia:Sandbox&oldid=974880776

And whoever it wants can use the following code for LibreOffice or OpenOffice:

{x + y + z} over {x {phantom +} {phantom y} + z}

Hence: LibreOffice and OpenOffice simply ignores the tag in the mediawiki-export extension and thus showing the complete x + y + z twwo times (above the bracket and under it).

For the mediawiki exporter extension code:

https://opengrok.libreoffice.org/xref/core/external/xsltml/xsltml_2.1.2.patch?r=2b383d19#1118

Progress:

- implement texvcjs change
- release texvcv version to npm (https://www.npmjs.com/package/mathoid-texvcjs/v/0.3.11)
- release texvcv version to npm (again) (https://www.npmjs.com/package/mathoid-texvcjs/v/0.3.12)
- release texvcinfo version to npm (https://www.npmjs.com/package/texvcinfo/v/0.5.7)
- update mathoid (npm, testcases)
- announce update to community
- deploy mathoid
- update documentation on ctan (not needed, but still outdated)