Compare the baseline alignment of integrals.
aka. What's up must come down.
\begin{document} \use[module=packages.math] \set[parameter=math.font.family,value=Libertinus Math] \begin[mode=display]{math} \sum_{k=0}^\infty \int_{0}^\infty e^{-kx^2}\,\mo{d}x \end{math} \end{document}
sile -o integral-alignment-sile.pdf integral-alignment-sile.sil
\documentclass{article} \usepackage{unicode-math} \setmathfont{Libertinus Math} \begin{document} \[ \sum_{k=0}^\infty \int_0^\infty e^{-kx^2}\,\symup{d}x \] \end{document}
xelatex -interaction=batchmode -halt-on-error -jobname data/integral-alignment-xelatex integral-alignment-xelatex.tex