>The justification for NaN not being equal to themselves is just bonk.

It makes a lot of sense to me. NaN indicates data has been lost. You did something and you stored the result in a number datatype but the result isn't a number. Data was lost. You lost the data and have only 'your answer wasn't a number.'

Comparing NaN with NaN is asking the computer 'we have two buckets that have overflowed, were their contents the same?' The answer is 'we don't know' which means, to err on the side of safety, the answer is 'no.'

No?