On Saturday, March 8, 2014 8:19:54 PM UTC-6, Tim Peters wrote

That would be true if the standard explicitly forbade extensions (any
optional operation or behavior not specified by the standard).  But
there are no standards like that ;-)  To comply with a standard, there
just needs to be _some_ way to "spell" all the behaviors the standard

The IEEE 854 1987  is just such a standard (Mike Cowlishaw's extension).

The generalized  IEEE 754 2008  standard might not have as much wiggly