The picture below says it all. Color highlighting with the soul
package prevents a correct rendering of the ff
ligature. Is there a way to fix this?
\documentclass{article}
\usepackage{color, soul}
\begin{document}
off -- offer \hl{off -- offer}
\end{document}
EDIT
cfr's answer below demonstrates that the problem disappears if the words are boxed with \mbox
. This will, however, break hyphenation and line-breaking, features that I would like to retain.