I've been thinking about this question a lot and I have another solution. You correctly wrote that Wikipedia articles have too much quality due to the editing.
But, the discussion (talk) pages are full of raw text data and are not prone to being edited, or even correct.
An example for the French language Open Data page (source):
Y a-t-il une raison pour laquelle le terme Open Data est utilisé partout dans l'article alors qu'il a pour titre Données ouvertes ? Je propose d'être uniforme dans tout l'article et d'opter pour la langue de ce wiki, c'est-à-dire le français. À moins d'une opposition claire, je vais procéder d'ici quelques jours. Dirac (d) 18 février 2013 à 19:48 (CET)
It's straightforward to download all the Discussion/Talk pages not only for articles, but also for Users, Files, Help, etc.
Download:
Wikipedia has a (massive) data dump at dumps.wikimedia.org (details). Be careful, the files are huge and won't open with most text viewers. It's best to have a programming approach for parsing the data.
The specific files you want are labeleled with something like enwiki-latest-pages-meta-current1.xml-p000000010p000010000.bz2
. The key part is pages-meta
and then some sequence for the individual files of the split data.
Parse:
The header of these XML files contains these (selected) keys:
<namespace key="1" case="first-letter">Talk</namespace>
<namespace key="3" case="first-letter">User talk</namespace>
<namespace key="5" case="first-letter">Wikipedia talk</namespace>
<namespace key="7" case="first-letter">File talk</namespace>
<namespace key="9" case="first-letter">MediaWiki talk</namespace>
<namespace key="11" case="first-letter">Template talk</namespace>
<namespace key="13" case="first-letter">Help talk</namespace>
<namespace key="15" case="first-letter">Category talk</namespace>
<namespace key="101" case="first-letter">Portal talk</namespace>
<namespace key="109" case="first-letter">Book talk</namespace>
<namespace key="119" case="first-letter">Draft talk</namespace>
<namespace key="447" case="first-letter">Education Program talk</namespace>
<namespace key="711" case="first-letter">TimedText talk</namespace>
<namespace key="829" case="first-letter">Module talk</namespace>
Wikimedia's guide to parsing the XML files, a guide to SQL import, and tutorial about how to parse with python: link and source.