I meant my comment more as a warning to readers than as a criticism of the article. When you've upgraded your mental model, don't stop and be satisfied -- see if there are more low-hanging upgrades. This is especially important if having recently improved your model biases you toward overconfidence (which I suspect is common).

To address your actual challenge...

Probability of correctness may actually be one dimensional. Though in practice it's worth keeping around what the big hunks of uncertainty are so you can update them easily if needed (i.e. P(my_understanding) = P(I_understood_what_I_read) * P(the_author_was_honest) * ... is easier to update if you later learn the author was a troll).

Degrees of correctness are more complex. "The geography of the Earth is as shown on a Mercator map" and "The geography of the Earth is as shown on a Peters map" are both false. They are both useful approximations. Is one more useful than the other? That depends on what you want to do with it.

There were other examples in the article besides correctness. "Every society imposes some of its values on those raised within it, but the point is that some societies try to maximize that effect, and some try to minimize it" and some maximize it with regard to their perspective on murder and minimize it with regard to their perspective on shellfish. "No one is perfect, but some people are less imperfect than others" and some people are imperfect in different ways from others, which are more or less harmful in different circumstances.