I understand evaluating someone's credibility as a proxy when I have no means of investigating something. I do not understand it when we are talking about scientific assertions, which must be falsifiable in order to be scientific in the first place.

That's of course a bit black/white to say, most arguments don't hold if you push them to their extremes like that. I said it because I believe (your) arguments like "saying that a person's credibility decides the truth value of the statement requires a causal relationship" are similarly black/white.

So yes, in a way the disagreement hinges on a very strict interpretation of the word "fact" versus a less strict interpretation.

It's also to save time in evaluating claims like these. If you've spent any amount of time arguing about pseudoscientific topics (or considered pseudoscience by some), you must have found that yes you can in theory evaluate all[0] (dubious or not) claims in logical, scientific, falsifiable manner. But at some point, especially in pseudoscientific-ish topics, there will be such a great number of claims[1] that you'll find yourself spending most of the time refuting spurious claims rather than actually getting any further.

At that point, you'll never get to the strict definition of the word "fact" (at least, about the particular claim that is the topic of interest), because the claims just keep piling on faster than you can evaluate them. Allowing for a bit less strict definition, allows you to prune the evaluations greatly, and at least allows you to get somewhere.

Now, that struggle doesn't seem to take place in this thread on HN, but according to user "dumbneurologist" it has taken place before elsewhere. And you're still taking that person's word on a matter of (merely claimed) reputation as well.

So yes, there is something to say for taking someone's reputation into account. But it's a pragmatic reason. If you had all the time in the world to dig into everything as deep as you want, you wouldn't strictly need to. But since we do not live in this perfect world, we can and probably should shortcut to the more interesting points of debate by including reputation.

That's the best I can argue this, I think :) It's still a choice, however. You can still choose to only accept strict facts (including "I don't know" when more specific strict facts are unavailable).

[0] ok, not all of them

[1] part of the definition of pseudoscience, where you keep adjusting or special-casing gaps in your hypothesis when it doesn't fit the data, almost necessitates this

We're not discussing the study but logic, so that's really not germane.

> It's also to save time in evaluating claims like these.

You can save far more time by ignoring them.