Treating null as an explicit category can be useful when:

Question

Accepted Answer

Missingness itself may carry signal and the model can learn a dedicated level — Sometimes 'missing' is a feature — model it as a level instead of crashing on NaN.

Answer

Missingness is never informative

Answer

You want to maximize silent NaN crashes at serve time

Answer

Using only pure linear algebra without data

Treating null as an explicit category can be useful when:

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