List of steps to reproduce (step by step, including full links if applicable):

• Go to the French Wikipedia
• Open for exemple https://fr.wikipedia.org/wiki/Nombre_p-adique.

What happens?:
Either with Legacy Vector or the new Vector interface, LaTeX does not display well (not formatting) in the table of contents.
For exemple:

• in the TOC I see: '"UNIQ--postMath-00000008-QINU"'
• in the title of section I see the LaTeX symbol instead

What should have happened instead?:
In the table of content, the text LaTeX should be displayed like in title of sections and in the text of paragraphs.

Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc.:
I've not tested other skins.