The general rule in Common is that you never use a noun to refer to a group of people. In Common, when you refer to some arbitrary collection of people bound by such factors as city or state of residence, nationality, ethnicity, race, religion, etc., you always use a modifier, never a term to do it. So analogising to English: always British, never a Briton, always Turkish, never a Turk, always Scouse, never a Scouser, always Jewish, never a Jew. As in English, it is actually grammatically possible to take either approach, but also as in English, only to a much greater extreme, there is a preferred style and a deprecated style, and a strong taboo against the deprecated style.

In fact, by the strict definition of a demonym as a noun describing the inhabitants of an area, Common doesn't have demonyms, or at least tries very hard not to, and in this discussion we're looking beyond words for groups of people living in a certain area to group names more generally. My intent is to examine a particular area of New World Order culture and Common prescribed grammar that intersects with demonyms and the naming of human groups.

English shows a little of the same tendency as Common in some specific circumstances, actually. In English, a similar pattern is sometimes seen as a euphemistic strategy in dealing with demonyms that have become terms of abuse in the mouths of some speakers. For example by saying 'Jewish person' instead of 'Jew', the speaker might be trying to avoid sending any possible signal of antisemitism. Some authorities on style have recommended this approach more generally, because it emphasises that the referent is a person first and foremost.

In Common, however, the prescription comes right from the Common Language Academy, na Akketemi na Xafen Zisse (AXZ) and is enforced by social taboos. The purpose is definitely not respect. Using someone from Cascadia as an example:

Correct:
Ny Kaskétijas atuin.
'A Cascadian person.'

Incorrect:
Ny Kaskétijaka.
'A Cascadian.'

If you said the latter, you would be understood. It is absolutely grammatical, in the descriptivist sense. But it is regarded as prescriptively ungrammatical, and using the second form comes across as both ignorant and subversive at the same time.

Ideological Basis

The subversive angle is important and gets to the real, very explicitly stated reason for this 'rule', which is political. One of the three pillars of the New World Order is 'na Ate Atuinysyn', 'the One People'. Under Globalism, humanity is supposed to be recognised as a unified whole and all tribal or national identities are to be repudiated as fake and toxic. Religious and non-Globalist ideological identification also comes under suspicion.

The Order specifically recognises rights inhering to humanity as a whole and to the planet, and to a lesser extent to individual humans, but rejects any kind of right inhering to groups, to the point of scapegoating group identity for all of the world's problems. The rule that demonyms must be modifiers (adjectives) and not terms (nouns) comes from the idea that a term could be an identity whereas a modifier is more distanced, it's just a description, and this pattern minimises the legitimation of any potentially suspect identities.

Whatever one thinks of this logic, it has social consequences. Whenever you forbid something, you make it attractive, so it adds emotional freighting and an edge of rebellion to the device of deliberately using a term as a demonym in defiance of this rule. Doing so can actually be an affectation to sound 'cool'. However. abiding by the rule is essential for polite speech or any speech which may come to the attention of the authorities. Common-speaking dissidents such as Humanists may deliberately affect term-demonyms amongst themselves as a signal of in-group affinity.

This ideology even comes into play in the Common word for 'demonym' itself, by which they are actually referring to the adjectival forms, not actual demonyms as we would understand them, 'na horolawt' or 'groupword', rather than the more sensible 'na horopoen', 'groupname'. This was consciously considered, and 'poen' was considered too noun-like and too humanising. For that reason, however, Humanists privately use the alternative 'na horopoen'.

The Exception: Proponents with -ka

There is a licit way you can derive a term for a member of a select and limited number of groups without triggering the taboo, and that is by adding the patienitive ending -ka to a base word for the primary association of such a group. Whether you can do this without attracting approbation is very much on a case-by-case basis and difficult to predict..

The normal, grammatically-comfortable way to derive term forms of demonyms in general would be exactly this approach of adding -ka to a term indicating a primary association of the group, although one could also use borrowed demonyms directly as terms, or just directly use the modifier-to-term conversion suffix -(y)n. Grammatically, this -ka form comes from the common idiom that terms for things that aren't typically very verbal are treated as intransitives verbs with the sense of 'be X' in a verbal context, which would give the -ka ending a 'one who is' kind of sense in context.

A typical example of  licit -ka is for words for people derived from some particular belief systems and ideologies. Ethnic and place names are more clearly beyond the pale as sources. If the belief system is clearly something solidly in Globalist good standing, like an actual Globalist faction X, X-ka is usually okay as a shorthand for its proponents. For example, a person who believes in uluafisa, or 'high belief', basically the conservative and authoritarian wing of the modern Globalist polity, can be comfortably described as an uluafisaka, although this is a touch informal. That informality can be part of the attraction for the elites using this term, though, as a form of in-group signalling.

You would generally not use this type of naming for a believer in something with a more problematic relationship with the Global state, except as an exercise in othering and drumming up antipathy. It would be a problematic move as a self identity. Even that usage is uncommon, as the authorities tend to try to avoid even backhanded validation of illicit identities. They could, for example, refer to 'nyr Kyrísfisaka', 'some Christians', in a negative context, but they are far more likely to say 'nyr Kyrísfisas trol', 'some Christian terrorists', or just 'nyr trol', some undifferentiated terrorists/dissidents.

Let's take Christianity as an example - Christianity operates both licitly and illicitly within the New World Order, but the Order regards Christians with suspicion, and consciously follows the model of twenty-first century China in the way they manage Christianity in that it's not illegal but it is kept on a tight leash. The Common word for Christianity is 'na Kyrísfisa', 'Christ-belief'. The modifier form is 'Kyrísfisas'. Here are some ways you could say 'I am a Christian':

Good:
We se an Kyrísfisas.
'I am Christian.'

Still good:
We se an y Kyrísfiasas atuin.
'I am a Christian person.'

Bad:
We se an y Kyrísfisaka.
'I am a Christian.'

Also bad, and stilted/non-native:
We se an y Kyrísfisasyn. or;
We se an y Kyrísfisa.
'I am a Christianity.'

Written Conventions

Demonyms derived from a place name, a belief system, etc. retain the capitalisation of their base form. If the base form is capitalised, the modifier form used as a demonym will be capitalised. Na Kaskétija, Cascadia, is capitalised, so Kaskétijas, Cascadian, is also capitalised.

However, there are a handful of licit, accepted modifiers that come from the names of ethnic groups and which can be used as a demonym but are not modern place names. These are words which typically entered the language before the modern period, got a high degree of currency, are associated with groups that are viewed as ' interstate'  in some way, and groups that the Global elite has generally positive feelings towards. It also helps if the word is used in well-established set phrases.

These words are never capitalised unless part of a set phrase that is regarded as a proper noun as a whole.

A good example is 'han', 'Chinese'. The New World Order has mythologised Chinese ethnicity as a sort of proto-Globalism, the Global elite has a lot of Chinese blood, and Chinese people are concentrated over multiple NWO States and ubiquitous globally. The modifier han is used in a number of vert well-established set phrases, including 'na Han Sef' or 'Chinese Hand', the unarmed combat system that all NWO elites are trained in at boarding school.

In the case of 'na Han Sef', 'han' is capitalised because the whole set phrase is considered a proper noun and capitalised, but normally, it would not be.

There are very few other examples of demonymic adjectives like 'han' being tolerated to persist in High Common. A couple of other examples are 'turki', 'Turk', 'hinti', 'Indian', and 'juro' 'European'. It is normal for these words to be problematic in some way or other when subject to scrutiny.