NaN is a standardized dynamic languages datatype governed by IEEE 754, this is not something to complain about as its behavior is part of the official standard and for good reason, as outlined in the standard.
To my understanding, NaN is a range of particular values (all exponent bits set to 1, mantissa nonzero) of the IEEE 754 float datatype, and its semantics are defined in the standard, including the "not equal to itself" semantic. If your language uses IEEE 754 floats and it has div or sqrt operations that don't raise exceptions on out of range inputs (which is something scientific computing people want very much, so it probably has them), then it must ensure nan != nan.