[MathML+useMathMLspacing:true] two adjacent fractions have no space

This was reported on the User Group.

Something like .

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mfrac>
    <mi>a</mi>
    <mi>b</mi>
  </mfrac>
  <mfrac>
    <mi>a</mi>
    <mi>b</mi>
  </mfrac>
</math>

will have the fraction lines touch (all outputs).

Up to v2.3, the rendering had some space between the fractions (and without useMathMLspacing that's still the case of course).

Was this an intentional change?