It is a bit annoying making queries in languages different from English. Words which are not usually considered important in the results such as "and" or "the", are treated differently when the language is not English, such as Spanish words "y" or "el". At least this is the feeling I have when using Duckduckgo.
It would be interesting if the search engine had some system to guess the language the query is being done, and discarding the common words in that language. This information may also be useful to provide better "did you mean" suggestions.