I add the diode because crutschow gets grouchy when I don't.

I may get grouchy at times, but not at that.

 

I see no reason for adding a diode if the input protection diode current limits are not exceeded since it adds unnecessary parts and expense, but if you are a belt-and-suspenders type of designer, it doesn't hurt.

Certainly, in the original circuit containing R4, I wouldn't add an external diode, only R4 it wasn't there. I am a belt and braces type!