I'm not sure that 404 is the correct response though. Wouldn't it be more correct for http://en.wikipedia.org/wiki/Gil_Prescot to return a temporary redirect to http://en.wikipedia.org/w/index.php?title=Gil_Prescott&action=edit?
That would be doing away with the "No page by exists by this title" page completely - do we want to do that?
You're right, I was confused. I was thinking the two pages were the same. They're similar, for users that aren't logged in, but not the same.
I guess 404 would be the right result for http://en.wikipedia.org/wiki/Gil_Prescott.
As for http://en.wikipedia.org/w/index.php?title=Gil_Prescott&action=edit, I guess it depends if you think action=edit really means action=editorcreate. If it does (and de facto, it currently does), then logged in users should get a 200 and logged out users should get...a 403 Forbidden?