While you're right, I think parent/OP's discussion is on how composable a language is with low semantic knowledge of the components, just going with the grammatical rules.

For instance in English you'll need to know if a subject is a third person singular or not to adjust the verb. Or even just singular vs plural for the adjectives and pronouns. And you'll need the gender in gendered languages (French, Italian etc)

In general, Japanese doesn't require that kind of care: the verb doesn't change, adjectives don't either, most of the words are unaffected if you swap semantically different parts.

> For instance in English you'll need to know if a subject is a third person singular or not to adjust the verb.

There is a suprising amount of subtlety here. What you need to known is if the subject is syntactically singular or not. Once you have that, it does not matter is the subject is actually singular. For instance, if you are talking to a single person, you say still say "you are" instead of "you is", because "you" is syntactically plural, regardless of its actual meaning.

This is very useful for generating grammatically correct sentences (or testing the grammar of existing sentences). The set of features that cause this type of inter-word agreement are called phi features (typically count, gender, person, and case). Since phi features are purely syntactic, you tag words with them just like you tag words with their part of speach.

In real speach, this can get weird, as it is possible for the same realized word to have different phi features depending on its sementic meaning. However, if all you care about is determining if a sentence is gramatical, you do not care if it means what was intended.

As an aside regarding Japanese, there have been some attempts to model Japanese politeness markers as a form of agreement; however, I have never found those arguements to be convincing.

> What you need to known is if the subject is syntactically singular or not.

It's a bit broader IMHO. For instance, plurals are handled as singular based on the semantics, even in written language. I liked how different authors handled the Olympics in wikipedia for instance

> The Summer Olympic Games, also known as the Summer Olympics or the Games of the Olympiad, is a major international multi-sport event

vs

> The modern Olympic Games (Olympics; French: Jeux olympiques)[a][1] are the world's leading international sporting events.

Same way a singular nouns will be handled as plurar if the speaker recognizes them as such ("The UN are planning a meeting")

There will be arguments on whether these sentences are grammatically correct, but I'd be more for the descriptive approach than the prescriptive one, as at the end of the day usage wins.

> attempts to model Japanese politeness markers

I kinda feel for them as it's the most evolving part of the language IMO. As people get used to a level of politeness, it loses it's status and a stronger form becomes needed. Basically there's a politeness inflation happening through the years, and it's all based on how people perceive it, so logic is also not an element of it.