Comment 22 for bug 610915

I would have to argue with either backing out 447788, or possibly adding a new setting, possibly on a site-by-site basis to allow case-insensitive username matches. Justin said in the earlier WONTFIX bug "We're kind of screwed no matter which way we do things, but I think the current behavior is better. Having multiple accounts (with different passwords) that differ only in case is already full of fail for a multitude of reasons, so I'm not really inclined to want to support that use-case."

The problem is that there are users WITH that use case, and in the current state, there is nothing they can do. With the previous state of the code, you could always delete the password entry with the wrong case and things would work as they should. Right now, if, for some reason, you need to have two usernames distinguished only by case, you CAN'T.