Re: "Why do you want feature X?" is always a really good start.
Agreed. Nothing at all wrong with asking a simple question.
Sometimes, the requestor just needs a bit of training to understand the requested feature is actually already available, perhaps in a slightly different form. Other times, the developer is enlightened to a use method not previously anticipated and the requested feature is worthy of addition. And then, every so often, one must patiently explain why the request cannot be granted because [valid reasons]
Biting the hand that feeds IT
