http://www.w3.org/Provider/Style/URI.html
Hence, if you rearrange content on a wiki, never delete the page - always use a PageRedirect, a PageAlias, or a PermanentAnchor. Even if the redirect might seem "silly".
To follow this policy rigorously you need ways to minimise the impact of redirects. For example, if you use a wiki's search engine, it should never return both a page, and a redirect to that page. You probably also want to minimise the impact of redirects in the BackLink view - never display orphan redirects, perhaps - or display them seperately from "proper" pages.