Earlier quoted context omitted.
In my experience the MathML support is still mediocre, especially on Chrome. https://fred-wang.github.io/MathFonts/mozilla_mathml_test/
That test page doesn't seem to use any features current Chrome doesn't support. Or do you just mean that the appearance isn't identical to the TeX rendering even if you use a font like Latin Modern?
It improved a little bit from what I remembered (on Chrome it had problems displaying multi-line brackets), it still has some inaccuracies tho