In the past, math was rendered as MathML. Even though I have "MathML with SVG or PNG fallback" selected in the preferences, I usually get SVG, but also got PNG at least on https://en.wikipedia.org/wiki/Fürer's_algorithm (a reload magically switched it to SVG), never MathML. Same problem with: https://test2.wikipedia.org/wiki/Mathematics

My web browser is Firefox 45.4.0 under Linux. MathML works on other web sites, such as Mozilla's MathML Torture Test page.

A quick test with Opera 40 showed the same problem.