It doesn't seem at all clear to me that persons B through E have additional evidence, no, and I would not adjust my confidence on that basis (unless they then indicate some form of evidence in their later statement after the "IAWYC and/but", of course).

However, I likely would increase my confidence in conclusion Y to some degree, depending on the statements these people made, because each person remarking on the conclusion without pointing out a catastrophic flaw in the reasoning is (weak) evidence to me that such a flaw does not, in fact, exist.