Take the template.tex example file from http://www.ctan.org/tex-archive/macros/latex/contrib/moderncv/examples and add these two lines:
\usepackage{fontspec}
\setsansfont{Linux Biolinum O}
Then run it with lualatex. Suddenly these thick bars get really slim. Why is that?

Example:
\documentclass[11pt,a4paper,sans]{moderncv}
\usepackage{fontspec}
\setsansfont[Ligatures=TeX]{Linux Biolinum O}
\moderncvstyle{casual}
\moderncvcolor{blue}
\usepackage[scale=0.75]{geometry}
% personal data
\firstname{John}
\familyname{Doe}
\title{Resumé title (optional)}
\address{street and number}{postcode city}
\begin{document}
\maketitle
\section{Education}
\cventry{year--year}{Degree}{Institution}{City}{\textit{Grade}}{Description}
\cventry{year--year}{Degree}{Institution}{City}{\textit{Grade}}{Description}
\nocite{*}
\bibliographystyle{plain}
\bibliography{publications}
\end{document}

moderncvin particular. I've posted a minimal example as an answer (although it's not exactly.) – Alan Munn Mar 21 '12 at 19:37