+++ This bug was initially created as a clone of Bug #410132 +++ There are some places in Reflow of MathML frames where child frames are moved after calling FinishReflowChild(). http://bonsai.mozilla.org/cvsblame.cgi?file=mozilla/layout/mathml/base/src/nsMathMLContainerFrame.cpp&rev=1.173&mark=1442#1422 The distance moved could be significant for some <mo> operators that are direct children of a <math> element (with no enclosing <mrow>). We should be able to shift the work that FixInterFrameSpacing does to the Place() methods. They could use another method to calculate the offset for the child frames, probably only necessary when aPlaceOrigin is true. There are about 13 different implementations of Place(), though. I hope the same issue with spacing around embellished operators in nsMathMLContainerFrame::Stetch() can be solved in the same way. http://bonsai.mozilla.org/cvsblame.cgi?file=mozilla/layout/mathml/base/src/nsMathMLContainerFrame.cpp&rev=1.173&mark=402,436-437#402