I suspected something of the kind, but wasn’t able to figure it out.
Thank you very kindly for the patience.
Yes, I have. Your link takes me to a blank page. (Viz. the menu you have seen in the image above on the left and a white page next to it.)
Settings > Writing > Writing Settings has the Markdown box ticked, but there is apparently no other option related to maths, latex, markdown or Jetpack.
The site is a clean setup. You can see it here.
Thanks.
