When the feature is not impissible. And you want the feature. And they want the feature. And we all want the feature. But no one can agree on exactly the right way to add the feature.
So we don't get the feature.
Discussion
What feature do we ALL want?
What if the right way to add a feature is more important for the future of the system than the feature everyone wants?
Alternative, there could be many different features and their implementations.
Because we don't want to fuck it up.