Shouldn't the '=' and the minus and the other signs be inside <mo>, rather than <mi>, because they are binary operators, not identifiers? TeX for example, makes

Shouldn't the '=' and the minus and the other signs be inside <mo>, rather than <mi>, because they are binary operators, not identifiers? TeX for example, makes a clear distinction in terms of how much whitespace it would surround operators with, vs. identifiers. In any case, I suspect MathML was intended as an intermediate computer-readable representation, not something that anyone would write by hand (MathJax can compile your LaTeX to MathML). I don't see what's wrong with an intermediate representation that's difficult to manipulate by hand. And unless I misunderstood the article, their point is that MathML is bad as an intermediate representation.