I'm not convinced that the reason English has capital letters is for legibility. Most alphabets don't make a distinction between miniscule and capital letters - in fact the only alphabets that do are Roman, Greek, Cyrillic and Armenian. But Hebrew, Arabic and the many alphabets of south and southeast Asia don't make the distinction.

According to the OED, it's "regional (chiefly Scottish)".

Douglas wrote
"In ‘The Concise Oxford Dictionary of Linguistics,’ P. H. Matthews defines the etymological fallacy as “The notion that the ‘true’ meaning of a word is the one to be expected from its etymology.” I don’t see how this can be used as an argument on either side of this pluralization debate. No convincing case has been made here."

OK, then don't call it the etymological fallacy. Call it the, I don't know, argument from Latin or something. The point is that it doesn't make sense to argue that words we've borrowed should be used, spelled, pluralized, declined, conjugated in the same way they were used, spelled, pluralized, declined, conjugated in the language they were borrowed from. For instance, it's a mistake to say that the "real" plural of "forum" is "fora" because that's how it was pluralized in Latin. Such a claim ignores the facts of English.

"I agree with you 100%, as shown in my previous posts."

Except that you presumably don't agree that the etymological fallacy is a fallacy, while I do. Language change is an observed fact of all languages. It is natural and inevitable. We can all complain about it, but we can't stop it. We've been using language for thousands and thousands of years, and it has been changing all that time. If language change was bad, then how can we still communicate.

Douglas wrote:
“The etymological fallacy holds, erroneously, that the original or historical meaning of a word or phrase is necessarily similar to its actual present-day meaning.”

I would interpret it a little more broadly: the original or historical usage or a word or phrase is necessarily similar to its actual present-day meaning. Not just the meaning, but how the word is used, including pluralization.

It's much older than the past year.

1598 SHAKES. Merry W. V. v. 239 This deceit looses the name of craft.
1667 MILTON P.L. II. 607 To loose In sweet forgetfulness all pain and woe.

"I am forgetting why we are arguing about “stamina”. It seems as though we both agree that using stamina as a singular form is incorrect."

No we don't. "Stamina" is commonly singular, as in “The stamina of the people was tested”. "Was" is singular. If "stamina" was plural, then it would be "the stamina of the people were tested."

My point is that all these words are plural in their original languages, but that they're singular in English. You can tell they're singular because they're followed by a singular verb: "stamina is", "erotica is", "data is", "candelabra is", "trivia is", "opera is", etc etc.

You wrote:
"Since the word “forum” is a Latin word used in the English language, I do not see how using the English-based plural system would apply."

This is the etymological fallacy. If we must apply the Latin plural system to all words borrowed from Latin, then stamina, erotica, opera, data, trivia, etc. should always and only be plural in English.

Douglas wrote:
"I’m not sure why these are even mentioned. What is the controversy?"

I mentioned all these words to show that their etymology as plurals in Latin or Italian or whatever is irrelevant to their use in English. hot4teacher seems to be arguing that a word should have a certain plural form that matches the plural form in the language the word was borrowed from. But the logical conclusion of this line of thinking is that all these other words, like opera, erotica, candelabra, paraphenalia, trivia, should therefore only be plural in English.

hot4teacher wrote:
"As for stamina, I have never personally seen or heard anyone use stamina as a singular form."

Really? It was first used as a plural in English, but began to be used as a singular in the 1800s.

"The stamina of the people was tested by a persecution that lasted for thirty years." - W.B. Thomson, 1895

I've only seen it used as a plural nowadays when referring to the stamens of plants.

"I would say that treating those words as singular would be wrong, especially considering that most of their singular forms are still used in modern English."

So you'd say that usage is irrelevant, that what matters is the words' etymology?

According to Merriam-Webster's Dictionary of English Usage, "data" followed by a singular verb is completely standard.

Another one is stamina... this is a plural noun in Latin, but it's singular in English.

"Cactus" is of Greek origin, but it was borrowed into English from Latin, just like "octopus" and "platypus" were. But "cactus" is different in that it would be pluralized "cacti" in Latin.

In any case, the idea that we must look to another language to find out how to use words is the etymological fallacy. To determine how English words are pluralized, it makes sense to look at how English writers actually pluralize them. In the case of "forum", the most common plural by far is "forums". As I said earlier, the OED doesn't even have any quotes with "fora".

Apparatus and status are borrowed from Latin fourth declension masculine nouns, so the Latin plurals are appar?t?s and stat?s. Agenda, erotica, opera, data, media, bacteria, candelabra, paraphernalia, trivia, graffiti are all borrowed from Latin plurals (Italian in the case of graffiti), so treating these words as singular would be wrong by hot4teacher's standards.