Wikification is good, but don't go crazy. There is such a thing as over-wikification — that is, the repeated linkage of the same word throughout an article.
Therefore, this community decided to link only the first instance of a word in each section of an article. If the article is not sectionalised, but has large, multi-sentence paragraphs, then wikify the word once a paragraph.
To give a practical example, we don't want the Doctor linked every single time we see it, but we do want it linked enough so that if we scroll down in an article we can still find the occasional link.