I wish MathML was better supported :(
Although, to be honest I'd rather have support for something closer to LaTeX. MathML is incredibly verbose, and certainly not something you would want to write by hand.
<p>
The triangle inequality states that
<la-tex>z \leq x + y</la-tex>.
</p>
Disclosure: I am my self an author of an alternative library MathUp[2].I don’t think it is unreasonable to ask authors that insist on writing in familiar syntax, that they use a tool that enables that. With native MathML authors are free to use whichever tool chain they prefer. Some authors will prefer graphical editing of equations, so they have their authoring tools set up that way. Others will just want to write their familiar latex syntax so they’ll put a:
<script src="./path/to/texzilla.js"></script>
in their document and write as before.