Words are currently separated by English punctuation like spaces, commas, etc., I suppose. This, however, makes it almost impossible to search for pages in other languages, like Chinese or Japanese where words are organized together without spaces.
Let's take this page https://movie.douban.com/subject/26897009/ for example. In the .subject div, there are some information about a TV show. If one were to search "制片国家" (country of production), the page would pop up in worldbrain's search. However, if "制片" (production) or "国家" (country) were searched, the page will not show up in the search results, since I believe worldbrain considers "制片国家" to be a single word.
Apparently, all the similar services like worldbrain I have tried have similar behaviors due to Latin (or similar) languages backgrounds. I sure hope this can be solved in some ways.