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> <mi mathvariant="normal">_ baseline _</mi> <mi mathvariant="normal">under script</mi> </munder> <mo>=</mo> <munder> <mrow> <mover> <mi mathvariant="normal">_ baseline _</mi> <mphantom> <mi mathvariant="normal">fail</mi> </mphantom> </mover> </mrow> <mi mathvariant="normal">under script</mi> </munder> </math>