Literal greek converts to wide-spaced MJX-TeXAtom-ORD

Created by: flying-sheep

Hi, the HTML renderer renders <span class=mrow><span class=mo>σ</span></span> with little space around it, but the MathML renderer creates <mrow class=MJX-TeXAtom-ORD><mo>σ</mo></mrow> which is far wider than the contained <mo/>.

i think it should rather render as <mi> like \sigma.