The most widespread example of MostlyWysiwyg is using the CamelCase to mark links in wikis. Other examples might be using "_" for _underline_, indentation for blockqutes, indented single asterisks for bullet lists and a row of dashes for a horizontal line.
On the other hand, MostlyWysiwyg as a principle breaks down when users wish to enter tables, in-line images, and links other than CamelCase. If what you want to get is a link to the Indiana University football program with the text "IU Football," you have to type something like this into the editor:
This can hardly be called seeing what you'll get.