If they like 418, they can add it to the spec. But this idea that it's been "consumed" is weird. It's like saying <blink> was "consumed" in HTML because two browsers used to support it. It was just an unofficial feature of popular vendor software, and is now officially disavowed.
Basically what we're saying is we're not going to implement 418 in the spec, but at the same time, we're not going to let anyone use it?