I agree that some of Vladimir's comments can apply to both meanings of "explanation," I was just trying to avoid conflating the two. I also think that most readers of pop-sci books generally wouldn't be able to tell if something's wrong, because most readers don't check multiple sources and use Google Scholar to find the papers being cited.

What I'm disagreeing with is Vladimir's original claim that "it's impossible to gain any real understanding of physics from such materials."

Almost all of the Sequences consist mostly of helpful explanations of concepts without going into full mathematical detail. I gave additional examples of non-mathematical explanations that improved my understanding in ways that informed my actions here, and wedrifid gave his own examples here. I gave one more here.

Because these all seem to be instances of improving someone's understanding of some idea in a useful way without them acquiring full mathematical understanding of that idea, I wondered if perhaps Vladimir was using an unusual definition of "understanding" such that for him "understanding" or "real understanding" only referred to detailed mathematical understanding. But in that case his original claim that "it's impossible to gain any real understanding of physics from [materials that don't impart a detailed mathematical understanding]" is basically tautological, and doesn't undermine the rationale for the original post ('Great Explanations').

Vladimir also seemed to claim that I can't have evidence about whether Copenhagen is correct or incorrect without understanding all the equations involved. But that seems obviously false, so I asked if I had misunderstood him.

I didn't downvote that comment, but might have, if I followed the conversation live. My thinking when I read it was: "He can't possibly really think that it is a homonym! So, for the sake of the argument he arrogantly (because that all caps spelling does show off some arrogancy) distorts reality and expects us to accept it?!"

But, now I see that this is too much of a correspondence bias. You probably just wanted to show that "explanation" has two different meanings, but in the head of the discussion just found a very bad example for your argument. Because "explanation" does have two slightly different meanings and this is relevant here. But let's be clear, these two meanings are close and in no way homonyms (as opposed to what you stated and what you clearly tried to present with the "fluke" example).

So, I think this comment of yours is bad and the downvotings were valid.

Edit: I didn't read the wikipedia article you linked when I wrote the above. I only ever heard/saw "homonym" being used in the sense of "two identically spelled and pronounced words with different meanings and of unrelated origin"; what Wikipedia calls "true homonym". In the more general sense the two "explanations" might qualify as homonyms (I am definitely not a linguist). But, your "fluke" example strongly indicated the more narrow (and, I think, more common) meaning. So, my reasons still stand.

My best guess: the comment seemed generally rude and "talking-down".

While I can see the motivation for typing "E-X-P-L-A-N-A-T-I-O-N", it seems to me like it would seem to people as somehow mocking, especially on a cursory read.