Therefore, the most important interface features must be on every page a user sees. For example, notice that RecentChanges is on every page on a UseModWiki as well as a link to the front page. However, since there is limited space on each page, some items must be placed at one level of indirection away--say a link to another page. The front page of MeatballWiki has links to important information, for instance. And so on as pages fill up past the limit of human comprehension.
(It's possible the density of linking on a page might be analagous to the target extent parameter in FittsLaw.)
But, putting everything at zero-depth might lead to bad choices. Was placing Wiki:VisualTour on every page a good idea? For WikiWiki, it probably was necessary to put any LinkGraphView on every page (due to lack of WikiBrowser), but it's probably not used very often because it's not very easy to use. So it becomes an artifact.
Sometimes I create navigational aids on sunir.org, such as the various IndexingSchemes. However, sometimes it's necessary to put those aids directly on a webpage. Suppose Cliff didn't want to put TwinPages support directly into the script, but he may put a link on the MeatballWiki link bar to do a MetaWiki search for TwinPages. Would this be as useful as StevenBlack's version of putting the links at the bottom of each page?
Whether or not TwinPages gets implemented here today is one thing, but there are many interface facets that definitely do not deserve to be placed on the site itself, but would be very useful to potential readers. Consider a LinkGraphView that didn't suck. This is where a WikiBrowser would be useful and brings up the value of such tools like TouchGraphLinkBrowser. Certainly many companies have products extending the InternetExplorer interface.