=== Steps to reproduce (on my wiki anyway) ===

On a wiki page make a link {[[Next Page]]}

Click on the green plus icon + "New" button to create a new page

Type the exact same string : {Next Page}

When you then try to follow the link from the original page it takes you to {Next_Page}}} and gives you a 404 error since the create page's URL used a space instead of an underscore
h1. Now create page again with the name {{{Next_Page}

This link now works (linking to the second created page)

=== Expected behavior ===

Both the contents of a wiki link and what is entered in the "Create a new page" UI should be considered the "name of the page". Neither should be considered the URL (one of the jobs of a wiki is to keep the user from dealing with site implementation details, one of which is the mapping from page names to their URLs)

==== Additional Note ====
I would expect that if the user clicks on a link to a page and that page doesn't exist yet, that they would be taken to the "create page" for that page name (which wouldn't actually create the page until they click "save") instead of being taken to a 404 page.