Only Topic Titles are searched, not posts. So this is quite fast but also means that only topics with similar titles, not posts, will be found.
- Similar topics will be sorted in order of decreasing relevance.
- Similar topic searches are not case sensitive
- Short words (less than 4 letters) are ignored
- Stopwords are ignored (the, and, some, etc.) full list of stopwords
- If a word is present in more than 50% of all topic titles, it is too common and is treated as a stopword and is ignored.