I don't read most of that the way you've read it. For example, Yvain said "Saying that there are likely flaws in mainstream medical research doesn't license you to discount any specific medical finding unless you have particular reason to believe that finding is false." Discount is much stronger language than simply reducing weight in the claim.

This argument violates conservation of expected evidence.

No it doesn't. It only violates that if in the alternate case where Yvain knew that almost all new studies turn out to be right he would point this as a success of the method. I suspect that in that counterfactual, he likely would. But that's still not a b or a c type violation.

Most of the reply to Nancy while potentially problematic doesn't fall into b and c. But I don't think you are being fair when you say:

Funny how he didn't see fit to mention this it his first post while he spent several paragraphs arguing for why satins are perfectly safe.

The standard of safe is very different than listing every well known side-effect, especially if they only happen in a fraction of the population. I don't see a contradiction here, and if there is one, it doesn't seem to fall under b or c in any obvious way.