Just recently I came across this. Should we be removing URLs that are no longer active? I never do this, and personally I would discourage it as I like all information past and present to be available there. I suppose there's extremely little use for deleted Pixiv accounts there when all of their images have been tagged (since I assume if they ever come back, it will have to be a completely new account), but this still strikes me the wrong way.
Updated by Katajanmarja