I've uploaded new make4ht version to CTAN. It contains new DOM filter: mathmlfixes. It should fix issues with nested token elements in MathML.

Installed patch, thanks as always, but leaving open since other issues remain (I believe).

for the record, further discussion in the thread starting at http://tug.org/pipermail/tex4ht/2014q3/001002.html.

As was pointed out by David Carlisle, there are spurious `<mi>` elements in the output of $\mathit{hello }\mathbf{world}$ when converted to mathml:

<math
xmlns="http://www.w3.org/1998/Math/MathML"
display="inline" ><mstyle mathvariant="italic"><mi

>h</mi><mi
>e</mi><mi
>l</mi><mi
>l</mi><mi
>o</mi></mstyle>...

it should be

<mstyle mathvariant="italic">hello</mstyle>

configuration of these commands is as follows:

\Configure{mathit}%
{\bgroup \Tg<\a:mathml mstyle mathvariant="\ifx
\bold:version\math@version bold-\fi italic">}%
{\Tg</\a:mathml mstyle>\egroup }%

I've found that generation of these spurious `<mi>` elements can be suppressed with `\PauseMathClass` command. There is Eitan's comment in tex4ht-mathml.tex:

-----------
Used to be

\begin{verbatim}
\Configure{mathrm}{\Tg<\a:mathml mi \mml:class="mathrm">\PauseMathClass}%
{\EndPauseMathClass\Tg</\a:mathml mi>}%
\Configure{mathbf}{\Tg<\a:mathml mi \mml:class="mathbf"
mathvariant="bold">\PauseMathClass}%
{\EndPauseMathClass\Tg</\a:mathml mi>}%
\end{verbatim}
------------

so it seems that `\PauseMathClass` was used in the past, but for some reason it is not now.

I created config file with `\PauseMathClass` in configuration of `\math...` commands, which converts example correctly to:

------------
<math
xmlns="http://www.w3.org/1998/Math/MathML"
display="inline" ><mstyle mathvariant="italic">hello</mstyle><mstyle mathvariant="bold">world</mstyle></math>
------------

If no issues are found and we don't find why `\PauseMathChar` isn't used in the configurations, when it was used in the past, I will make patch for the literary sources.