> One of our known scientific facts is that we know our understanding physics is incomplete (namely, QCD and GR are incompatible), so obviously we can never put 100% confidence into Carter's negative claim.

By this line of thinking we can never put “100% confidence” into anything at all.

But our understanding of physics will never be “complete”, therefore this is just a cheap argument to say we must assign every claim a non-zero chance of being true.

> This is just Epistemology 101, and totally uncontroversial.

You’re mincing claims, jumping from obscure physics to “Epistemology 101” and trying to lump it all together as “totally uncontroversial”, but it’s really just an attempt at moving the goal posts with fancy language and big words.

It doesn’t change the fact that the original claim clearly has some factual inconsistencies, such as the way the date of the encounter doesn’t even match other records of the event or even appear to be in the same season at which the event occurred, or that none of the other people present appear to have come away with similar observations.

Talking about physics and GR and QCD and Epistemology 101 doesn’t change anything. It’s just superfluous jargon.