A Suggestion for MediaWiki, useful for multi-language wikis, based on my experience from Wikipedia.
The idea is to add multi-language search (exact) matches on the left panel of pages showing search results. Though this may not be feasible with the current data architecture within MediaWiki, there's no reason why it should be impossible to implement.
That would ease the look for information for people who can speak several languages. That would also stimulate the creation of articles by translation of articles from other languages. As a reminder, a big part of mankind speaks two or more languages, I'd say more than half of it.
Let's see an illustration. Figure 1: what you get when you search for "xades" on the English Wikipedia.
Figure 2: what you get when you search for "xades" on the French Wikipedia, no direct results.
Figure 3: What I suggest adding onto the search page (the French one, in this case).