The comment/CDATA prefix/suffix surrounding code within <script> blocks in multiple places in Dokuwiki (such as _tpl_metaheaders_action()) causes invalid syntax errors in IE (version 9 and I believe 8 as well) and prevents the code from running.
For example, creating a script block in a plugin using the handle_tpl_metaheader_output() function and specifying a non-empty _data member (as in the mathjax plugin, where a user ran into this) will create a script block with contents like:
The same CDATA prefix/suffix shows up in a few places in inc/html.php as well. I haven't experienced the issue outside of the mathjax plugin, but I expect it produces the same error when it appears in other places.
1) Install the mathjax plugin (alternatively: create a new plugin that creates a script block with inline code)
2) Load any wiki page with IE9