Both of the uses in the article seem to be deprecated, though, and not used to imply "impairment". Kind of a dumb joke. What's next, "HTTP 69: Loop Detected Between Input And Output"?
And yes, that would be way more useful.
...that sounds like an example use case for the proposed status code.
420: Requester Impaired - Infinite loop
It would allow you to signal to the requester that while their individual responses are fine, their session behavior is incoherent.