I think your reasoning is correct: there is no efficient way to do this while storing only a hashed password. Also, it would be out-of-character for the minim

I think your reasoning is correct: there is no efficient way to do this while storing only a hashed password. Also, it would be out-of-character for the minimalism of the site. I'd go with "joke", although I'm not sure whether it's intended to be "silly" or "cruel".