"\section{The command line parameters} \index{parameters}" is the
workaround which I currently use. It works mostly ok, but has different
disadvantages:

1. The generated anchor is not completely correct. It is on the line
after the section title, but it should be on the title itself.

2. The source now needs to contain the index value two times. Before
I used the macro
\newcommand{\Index}[1]{#1\index{#1}}
to prevent this.

3. The original tex sources do not compile out of the box. Not a problem
for me, but not what one would like to have ideally for a general
tex to html converter.

Unfortunately that workaround does not work correctly. There is then for
every occurrence of the section argument an own index entry, which is not
what one wants.

Consider the following slightly extended example

--------------------------------------------------
\documentclass{report}

\usepackage[tex4ht]{hyperref}
\usepackage{makeidx} \makeindex

\begin{document}

\tableofcontents
\cleardoublepage

\section{The command line parameters\protect\index{parameters}}
\label{commandline}

Text.
\cleardoublepage

\printindex

\end{document}
--------------------------------------------------

Here the index entry of "parameters" contains in addition to the correct
"2" for the section start a wrong "1" for the table of content.

I compiled this example with:

htlatex test.tex
tex '\def\filename{{test}{idx}{4dx}{ind}} \input idxmake.4ht'
makeindex test.4dx
htlatex test.tex

Compiling the following code with "htlatex test.tex" results in a
"TeX capacity exceeded". Compiling with latex and pdflatex in contrast
works fine.

--------------------------------------------------
\documentclass{report}

\usepackage[hypertex]{hyperref}
\usepackage{makeidx} \makeindex

\begin{document}

\section{The command line parameters \index{parameters}}
\label{commandline}

Text.

\end{document}
--------------------------------------------------

The error message is
--------------------------------------------------
! TeX capacity exceeded, sorry [input stack size=5000].
\:nbsp ->\leavevmode
\special {t4ht@+\string &{35}x00A0{59}}x
l.9 \label{commandline}
--------------------------------------------------

Moving the \index{} outside of the \section{} argument or removing
the \label{} allows to compile the code.

I am using texlive-tex4ht-2011-13.5.1 under texlive-2011-13.5.1
on an openSUSE 12.2 system. tex4h.sty prints "version 2008-10-27-17:23".