That's not true at all. The article says that you have three Facebook passwords, not that the passwords are case-insensitive. The three passwords in question a

That's not true at all. The article says that you have three Facebook passwords, not that the passwords are case-insensitive. The three passwords in question are the password you typed, that password with its case toggled, and that password with the first letter converted to uppercase. In other words, if your password were "asDF", then "asDF", "ASdf", and "AsDF" would be valid passwords, but "asdf" and "ASDF" would not. Most likely, hashes of the password you typed and the two transformations are stored separately. Or only the hash of the original password is stored, and the transformations are done as part of the login process.