The OP of How to project a vector onto a very large, non-orthogonal subspace has written to complain that the question was closed unfairly. The question is too far from my area of expertise to be confident the question is appropriate for MO, but it's certainly not clear to me that it isn't. I'm hoping some people who are in the know can weigh in here.
My own leanings are towards reopening, because the question seems to lie in an area that could stand greater representation at MO. But I'd defer to more expert opinion.
Update: The question has now been reopened.