Here's my MWE:
\documentclass{article}
\usepackage{unicode-math}
\newcommand\closure[1]{\overline{#1}}
\begin{document}
The intersection of the closed ball $\overline{B}(1)$ with the closed
ball $\closure{B}(2)$ is the same as the intersection of the closed
ball $\closure{B}(2)$ with the closed ball $\overline{B}(1)$.
\end{document}
This is what I'm seeing (with xelatex):

Note the extra space before "B(2)" and the missing overline.
The problem goes away when I comment out \usepackage{unicode-math}.
