The page https://en.m.wikipedia.org/wiki/User:Beland/math_bug renders correctly when viewed in a desktop browser. It seems to render fine on an android phone, in chrome and Samsung internet browser.

Image description pages like https://commons.wikimedia.org/wiki/File:Peano_intersection.png#/media/File:Peano_intersection.png do not render correctly in Firefox/Chrome running on windows 10, the equation is not displayed.

Yes, you need to click on the image to see the bug, which takes you to e.g.: https://en.m.wikipedia.org/wiki/User:Beland/math_bug#/media/File%3AWikipedia-logo-v2.svg (notice the broken square root in the description at the bottom of the page).

That is because the MMV description is not a wiki page. You can also not put an image inside a caption for instance, or a graph, or a map.

See also: T256528

Right; images and graphs and stuff generally aren't needed in captions. But sometimes it is necessary to put complicated math expressions in captions to explain what is being visualized.

This bug seems to have become worse: instead of showing the content of the math tag as code as in Beland's original description (not always easy to read but still sometimes useful) it is quietly dropped completely (at least in the Monobook/Safari combination, I did not check other browsers/skins). Click on the lead image at https://en.wikipedia.org/wiki/Bump_function : the image caption turns into the completely useless "The graph of the bump function where and".

Can you add a screenshot?

@Kusma: Please add a screenshot.

Sorry, did not notice this. First screenshot: article with image with complete caption. Second screenshot: What happens when I click on the image. Monobook on Safari.

I see the same thing not-logged-in (so Vector2022) on Firefox, for what it's worth.