If you hash, with or without salt, on the client for changing the password, you'll also need to hash identically when checking it (i.e. for login). In effect, the hash becomes the password; even if the plaintext is never leaked the first-level hash is just as good for access.
Right, but if a hacker releases a password dump for site X, no one has your password in plaintext, just the log in hash. That said, that solution requires JavaScript.
Yes, but then the attacker can ignore your JavaScript and just send the hash value they got from the dump. If you calculate hash(password) and send that for comparison to the hashed password stored in the user database, then hash(password) is your password from then on.
