Thanks for the feedback, everyone.
@Andaith: The point is that having any automated password reset mechanism undermines the security of the entire system. An attacker is able to modify the password without having knowledge of it. The relationship of Web application authentication to email accounts is a separate discussion, though an interesting one.
@AdriaanNel: Both techniques should work as expected with pre-filled password fields. This is important not just for browser-level features, but in the case of validation where a user is redirected back to a form to supply additional information.
@rosaiani: Yes, a framework could make this easier, and the article mentions that. But JQuery is just one option (everybody has their favorite), so I wanted to demonstrate the concept without marrying it to a particular framework.
@Chibu and @juanojeda: The point about editing an arbitrary character in the progressive masking technique is a good one. The function could probably be made more sophisticated to handle this situation. However, this does seem to be a pretty unlikely behavior.