The `denied` key only appears if the user, upon reaching the Twitter login page, clicks "cancel" to deny authorization. If this happens, Twitter returns `denied=$token`.
So yes, we want to check whether the problem is that the current user has clicked cancel, or that a different user has clicked cancel and this is being returned to the wrong account - which could happen if the user logged out of Dreamwidth in another tab while they were at the twitter login screen.

I've added some comments to explain this.