I think that was the case when I came up with a user style to display the MathML. Perhaps they leave it only for the accessibility benefits? Either way, SVGs displayed black-on-black, so I added this CSS and it’s now fine:
.mwe-math-mathml-a11y {
opacity: unset;
position: unset;
clip: unset;
overflow: unset;
}
.mwe-math-fallback-image-inline {
display: none;
}
dl dd {
overflow: unset;
}