The -- is special to TeX and was printing as just -.
\begin{methoddesc}{handle_comment}{data}
This method is called when a comment is encountered. The
\var{comment} argument is a string containing the text between the
-\samp{<!--} and \samp{-->} delimiters, but not the delimiters
+\samp{<!-\-} and \samp{-\->} delimiters, but not the delimiters
themselves. For example, the comment \samp{<!--text-->} will cause
this method to be called with the argument \code{'text'}. It is
intended to be overridden by a derived class; the base class