I see where the confusion comes from then, thanks for linking some kind of source at least.
I think we need to understand what the problem statement here really is because there’s clearly some disagreement. To do so, we need to identify exactly what result you are trying to achieve (and not just in this conversation, but in the bunpro grammar point in general).
Your claim is that there is only one な with three different usages.
Let’s assume your claim is correct and that, indeed, there is one single な. You already acknowledged (and this is also supported by your linked article) that in 古文 there are three different and very specific usages of it (in modern Japanese we can identify only two of those so let’s focus on them from now on):
- Imperative negative (するな！)
- Emotional/emphatic particle (美味しいな〜)
What do you think is the benefit from the point of view of a language learner in thinking that these two particles are the same? Let’s analyse what this actually entails in reality:
- The meanings are very different
- Their grammatical usage is very different (they attach to different parts of speech, they allow different parts of speech to attach to them differently, etc)
- They are not interchangeable
Is there anything I’m missing here? How is calling these two particles “the same” going to benefit anyone?
Maybe I can be convinced this is a good choice if you put up a convincing-enough argument to support it from the point of view of a learner.
On the other hand, if you want to stick to this explanation strictly because you want to fit one specific model of your grammar to the whole site, then we have to look at this from a different perspective. You claim that it is the same particle used in different ways. Now you need to define what it means for two particles to be the same.
If you were to ask me, the following is the definition I would be willing to accept.
Two words/grammar points/particles can be considered the same if they fit at least one (or more) of the following criteria:
- They mean the same thing
- They connect to the same parts of speech (noun, verbs, certain conjugations, adjectives, etc)
- They have a shared etymology / they come from the same origin
Now, these two な particles clearly don’t mean the same thing, so the first point is already out.
Point 2 is also out because these two particles are used differently and connect to different parts of speech: The imperative negative connects to 終止形 of verbs (するな！ etc) while the emphatic な can go after non-verbs (美味しいな, etc). On top of that, what is allowed to come after the な itself differs as we saw in my example earlier (よな vs なよ , etc).
The last point we need to look at is the etymology. Your link talks about 古文 and how there’s three different usages of the 終助詞 「な」. Note that it does not claim that all three of them have the same origin nor come from the same word/stem/root/whatever. It’s simply stating that there’s three types of な particle with very clearly different usages (see point 1 and point 2). This is neither necessary nor sufficient evidence that they share the same etymology (Actually many other sources seem to claim they do not, see Etymology 2 and Etymology 4 here). Truth be told, wiktionary might not be a reliable source but so far I haven’t seen any other strictly etymological source that supports your claim. And just to be clear, let me repeat again that the article you shared does not explicitly mention that and is not a source that would support this claim.
So, under these definitions, you cannot claim that those two な are the same particle, just like you cannot claim that 漢字 and 感じ are the same word because they are both かんじ and are both nouns. They have a different meaning, a different usage, and a different origin.
In conclusion, myself personally I’d love to find out that indeed these two な usages stem/originate from a single shared origin (although I still refuse to consider them “the same particle” in modern Japanese but that’s just a matter of perspective), however you need to show a bit stronger evidence than what you shared so far. But, besides that, you still need to ask yourself what benefit does this bring to a learner? And the answer to that is literally none. I can’t honestly see any positive aspect in telling someone that するな and 美味しいな are “the same particle” other than some kind of weird pride in your own internal mental model of grammar (that doesn’t seem to be that well rooted in reality). It’s just doing your own community a disservice.
Extra
So I admit I’m not a 古文 or 漢文 expert but I’ve done some more digging and found some stuff that might interest you. For example this page talks about various 終助詞 including 哉 (かな → だなぁ). Looking further into 哉 on kanjipedia we can find:
①かな。…だなあ。詠嘆の助字。「快哉」
(seems like there might not have been a distinct difference between かな and just (だ)な in 漢文? not sure)
On the other hand if we want to look into the prohibition usage as negative imperative, we can find stuff like this. The example is pretty poignant too:
「…すること」と呼応して禁止を表わす漢文訓読語。…するな。…することなかれ。
and especially the example sentence:
「雷の神、人夫(おほむたから)を犯すこと無(マナ)」
Which seems to imply it might have been 犯すこと無 → 犯すことな → 犯すな but this is entirely my conjecture so don’t take it as a fact.
Regardless, if my understanding is correct and emphatic な came from 哉 and prohibition な came from 勿 then to me that’s some pretty strong evidence that means they are quite different. This is still a big if though.
NOTE: I had more links and references but bunpro forums consider me a “new user” despite being on this platform for 4+ years (but never the forums), so I can’t link more than 3 links per post. Feel free to ask if you want more and I can provide more.
). In this particular case we still strongly feel there is a connection to the 聞き手 - 話し手 relationship even in the prohibitive な and will continue to research and build upon it.
