In the LaTeX output, the fontenc package is used as
\usepackage[T1]{fontenc}
I found there was bad formatting for a string of commas in a fixed width
font. This is a minimal example:
\documentclass{book}
\usepackage[T1]{fontenc}
\begin{document}
\texttt{abc,,,,xyz}
\end{document}
I've attached the output as an image "clip.png". If I remove the fontenc
line, it looks like "clip2.png".
It appears in whatever font fontenc is using, there is a ligature that
transforms ,, into a single character.
