Formatting of right hand side of equation should be identical to formatting of left hand side
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"> <munder> <mrow> <mover> <mi mathvariant="normal">- middle -</mi> <mi mathvariant="normal">top</mi> </mover> </mrow> <mphantom> <mi mathvariant="normal">fail</mi> </mphantom> </munder> <mo>=</mo> <mover> <mrow> <munder> <mi mathvariant="normal">- middle -</mi> <mphantom> <mi mathvariant="normal">fail</mi> </mphantom> </munder> </mrow> <mi mathvariant="normal">top</mi> </mover> </math>