The way that I previously installed my customized MathJax was as a sub-directory of mathjax-latex/.  A side effect of this is that a purposeful or accidental upgrade of the mathjax-latex (wordpress) plugin, will obliterate that MathJax/ download (and default.js customization).

I’m using GoDaddy wordpress hosting (I probably should have used an amazon ec2 instance, which was more flexible and probably would have been cheaper). GoDaddy now offer ssh (not just sftp) access, which makes this reconfiguration much easier.  I couldn’t find a zip for the Mathjax distro anymore, but this worked:

cd html/wp-content
git clone https://github.com/mathjax/MathJax.git
cd MathJax
git checkout 2.7.9
cd config
vim default.js

You can see what my default.js looks like with:

curl https://peeterjoot.com/wp-content/MathJax/config/default.js

that has a big LaTeX Macros block, equivalent to a subset of my peeters_macros.sty

Installing the customized MathJax tree this way means that I need only set the mathjax-latex CDN path to:

https://peeterjoot.com/wp-content/MathJax/MathJax.js