I just came across the following weird bug. In this MWE:
\documentclass{article}
\usepackage[libertine]{newtxmath}
\usepackage{libertine}
\begin{document}
These are the same \(\int \displaystyle\int\); but these aren't \(\sum \displaystyle\sum\)
\end{document}
the size of the two integral signs turns out the same when the code is compiled with lualatex. On the other hand, the sums do have the correct size.
Whenever the code is compiled with xelatex everything goes well and the sizes are the expected sizes.
The order of the inclusion of the packages doesn't matter.
If one removes either of the packages the problem is not reproduced.
What's going on?
