How to describe this bug?

[Aleksey Khudyakov]

On 13.07.2012 19:27, Brandon Allbery wrote:
> On Fri, Jul 13, 2012 at 7:29 AM, Aleksey Khudyakov
> <alexey.skladnoy at gmail.com <mailto:alexey.skladnoy at gmail.com>> wrote:
>
>         Num inherits from Eq, so Float couldn't have an instance for Num
>         if we
>         didn't have that Eq instance.
>
>     No more since GHC 7.4. But Eq is indeed superclass of Ord and it Ord
>     is used a lot.
>
>
> ...but Float's Ord instance is even more dubious than its Eq.
>
What's wrong with it except for NaN? NaN surely breaks every law but 
otherwise it's OK.