The MathML operator dictionary makes ( [ { | stretchy, so a plain bracket grew
to the tallest thing in its row — next to a sum with a fraction, C(b) came out
in full row height. Only a fence node emits stretchy brackets now.
A formula node stores only its LaTeX source; the MathML on screen, the ODF
formula object and Word's OMML are derived from it, and both importers parse
foreign markup back into that source, so an imported formula stays editable.
Word documents were losing their formulas outright: m:oMath sits beside the w:r
runs in its own namespace, past convertInline's `namespaceURI !== W` guard.
Steffen Becker