A plausible mechanism is not an outcome, and this class is the textbook example.

Same here.

Cold storage, light protection, date on the vial. Boring, removes half the variables.

Three questions kill most of the confidence in a thread like this: sample size, blinding, who paid.

An inconclusive account is useful if it stops the next person mistaking a story for a controlled comparison.

Narrow conclusion.

Same here.

An inconclusive account is useful if it stops the next person mistaking a story for a controlled comparison.

Is a baseline blood test really necessary before starting something like this?

Same here.

How long before you can reasonably say something is or is not doing anything?

I would take the narrow conclusion. Broad ones are more interesting and less true.

Same here.

Stupid question: how do you know whether what is in the vial matches the label at all?

An inconclusive account is useful if it stops the next person mistaking a story for a controlled comparison. Nausea on an empty stomach was my main issue with vitamin K2 too.