If limited to proposed technical fixes for known problems, for example in Wikipedia, where should such documents be stored? Note that this is not about Mediawiki as such, its mostly about observed problems in the use and implementation of the software in specific Wikimedia projects.
It seems to me like the documents contain three parts; a problem description (what), a resolution (why) and proposed solutions (how). It must be simple to link to both the mailing archives, to svn, to the mediawiki site, to bugzilla, to the projects, etc. Basically a wiki, and it seems to me like this is something for Meta, but could go on the Mediawiki site too.
The technical discussions could be on Bugzilla, but there should be a statement about important threads under the section for proposed solutions. This makes it more simple to find the discussions. I believe Bugzilla is to alien for most wikipedians, even if it is a good tool for the developers.
I made an example at Meta (http://meta.wikimedia.org/wiki/User:Jeblad/demo)
John