Is it true that nouns meaning nationalities that end with "-ese" or "ish" don't need an indefinite article

Question

so that it's wrong to say "I'm a Chinese," "I'm a Japanese" or "I'm a British, " "I'm a Scottish," while it's ok to say "I'm Chinese" or "I'm Scottish?"

I got the information from here:
http://www.eigo-nikki.com/article/13144551.html

Answer 1

My understanding is that you don't use an indefinite article when you say your nationality (in English, of course...), regardless of the way the word ends; for example: "I'm Costarican", "I'm Italian", "I'm French", "I'm Norwegian", and so on...

Answer 2

Well, here's the thing, in ALL of these cases, these words aren't Nouns, they are Adjectives. Now, can these words be nouns sometimes? Yes, but only in specific cases, such as if you talk about the people in General like:
"The British and the French always fought for many centuries."
However, When you are talking about an individual, the noun is different. It's like saying the difference between the Plural and the Singular. Like so
Singular: Britishman/Britishwoman Plural: The British
Singular: Chinaman/Chinawoman Plural: The Chinese
Sing: Scotchman or Scot Plural: The Scottish.

Now, you see that this is when those words are Nouns. But Also remember that the -ese and -(i)sh endings are also adjectives. Look:
A British car works just as well as a Japanese car.
I downed a lot of Scottish beer in my day.
Now you see these are Adjectives. Well remember that adjectives can also be used with the verb TO BE. So when you say, "I'm British." British isn't a noun, it's an adjective.
If you want the noun, say "I'm a Britishman."

So is it true? No, the nouns showing nationalities should have an article.

Answer 3

That is correct. But when you are talking about a nation as a whole, you would say "The Chinese eat more rice than the English". Also when referring to Scottish people you say "The Scots like haggis" or "she is a Scot" (as an alternative to "She is Scottish"). Never use "Scotch". That is reserved for whisky. We really do have a funny language!