I believe the SVG file has a transparent background, but the img tag has style="background-color:white". Some browsers honor the background-color setting and show a white background behind the equations, even in dark mode. Some do not, and so the equations appear as black-on-black.
It would be better if I altered the SVG image itself to set the background color, but I don't know how to do that. Suggestions are welcome.
I don’t have a reference, but I believe I read an article explaining that this theory was based on selective data and that in fact dogs have no direction preference.