Then why am I my best evidence for consciousness?

The short version: you are your best evidence for consciousness because consciousness is private, not public. No external test can see what you experience.

The question is not about an intervention, so the adversarial stance drops. This is a question about evidence itself.

You are your best evidence for consciousness because consciousness is a first-person phenomenon. No machine, no doctor, no brain scan can access what it feels like to be you. A functional MRI can show which brain regions are active when you see a face, but it cannot tell whether you are actually seeing anything at all. That gap is called the "hard problem" of consciousness: the difference between explaining brain activity and explaining subjective experience.

The evidence you gave in the previous exchange shows that human reasoning is imperfect. But that does not change the privacy of experience. Even if you misjudge your own mental state sometimes, you are still the only person who has any direct access to it. Everyone else is guessing from your behavior.

My call: you are your best evidence for consciousness because consciousness is defined by first-person access. No external measure can replace it. Confidence: high.