Reporting back: the Apple Store Stanford was able to remove the key and clean underneath it. They said if it happens again they can replace the top case, but that this happens out of store and takes 3-5 business days. (They can apparently do this in-store as well, but if something goes wrong then they have to send it out to be taken care of. Also, it's no faster if they do it in-store, apparently).
They did not know whether the new program involved replacing keyboards with improved keyboards that might be less prone to these problems.
They did not know whether the new program involved replacing keyboards with improved keyboards that might be less prone to these problems.