MathML is a failed web standard
Blargh.  It annoys me that MathML was even a thing.  We've already had a perfectly-fine and widely-used markup language for mathematical formulae; it's called TeX.<p>Ideally, I'd prefer that HTML5 include a <math> tag, or something similar, that takes TeX as input and produces formatted output.  A side benefit would mean that every browser, and every system, in the world would have TeX installed!<p>At least MathJax can take TeX as input.