It looks like you're missing the tidy configuration file.
The default one we provide is in the extensions module, in extensions/tidy.

dbw wrote:

Sorry if this is a stupid question, but I have been searching high and low
(Google, MediaWiki, MetaWiki) for a default tidy configuration file in the
extensions module, and have found nothing. Not even really a mention of one.

Where is this meant to be obtained from?

FYI, Tidy is working, and it is using the configuration file that is the default
for Tidy on the server itself. The configuration file exists, it is in the
default location that tidy looks for the configuration file etc.

Ahh, think I have finally found it:
http://meta.wikimedia.org/wiki/Data_dumps#Common_Problems_and_Solutions under
the heading "After I run importDump.php or mwdumper, the articles are messed up.
Templates are skewed and do not display properly. what can I do?"

Seeing if that is appropriate and fixes the issue.

dbw wrote:

That appears to be it!

Damit, something so simple. I have updated the various locations where i have
made comments about this, that a tidy.conf needs to be included. Will update
some details in the manual about tidy to note that as well.

Note that I've moved the default location for the tidy.conf into
includes/tidy.conf, so as of MediaWiki 1.10 it won't be necessary to fetch
extensions files separately for this.