Comment by Rexxar
Something like that could probably be implemented by storing multiple hash of some automatically modified version of the password. For example, if your password is "PassWorD" they can additionally store the hash of the lowercase version of the password. So if you change it from "PassWorD" to "paSswOrd", they will see it has the same lowercase hash than the previous one without knowing it.
This doesn't seem practical at all. The combinatoral explosion would make the storage requirements impractical for everything but the absolutely most trivial cases like incrementing a number as the very last digit. Even in your simple example you're talking about storing 256 different hashes just to catch one possible mutation on a way too short password.