Steps to reproduce (on Wikipedia, but I think it is a problem with MediaWiki):
- Go to your user preferences page and click on the search tab.
- Uncheck the (Main) namespace and check the Wikipedia namespace.
- Click save.
- In the search field on the left panel, type "columns" without quotation marks.
You are taken to the (Main namespace) article, Column
Articles in the Wikipedia namespace that explain how to format wiki text into columns.
It seems that the "I'm feeling lucky"-esque functionality is interfering with the namespace exclusion.