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.