I just realized that my current version of the customization system is generally doing this:
The tree on the right I don’t want because there is no extraction happening. The top S is licensed by the wh-ques (filler gap) rule in both trees.
The question is why is the tree on the right happening. Something should be ruling it out, and I am not sure how deep in the grammar. I am not actually seeing any relevant differences in the matrix core (between my version and the trunk), so, might be in the wh-ques rule itself? But it does say that the head daughter should be slashed. So I am a bit confused. The head daughter in this case is head-subject.
What should be ruling out the tree on the right, in principle? I would think it is a SLASH <! !> somewhere (up the hierarchy of the decl-head-subj?..)