On Wikipedia (and MediaWiki in general), is there any way to search for a phrase within the contributions of a specific user? As a proof-of-concept, I want to find a way to search for the word "Wikipedia" within the contributions of the user "Jimbo Wales": http://en.wikipedia.org/wiki/Special:Contributions/Jimbo_Wales
There isn't a tool available to easily retrieve the information you need, but I strongly recommend that you download a copy of the database and analyse the contributions of the specific user that you need.
Alternatively, you can query the database directly using the Wikimedia Toolserver (if on Wikimedia projects) or the master server database the wiki is on, using the conditions of the user_id and page content to search.
Can't really help much, but there really isn't such a tool currently available.