Similar to SN 1.25 cited in Dhamma Dhatu's answer, there's a Milindapañha which begins,
King Milinda went up to Nàgasena, exchanged polite and friendly greetings, and
took his seat respectfully to one side. Then
Milinda began by asking:
“How is your reverence known, and what sir, is your
name?”
“O king, I am known as Nàgasena but that is only a
designation in common use, for no permanent individual
can be found.”
Then Milinda called upon the Bactrian Greeks and the
monks to bear witness: “This Nàgasena says that no
permanent individual is implied in his name. Is it possible
to approve of that?”
The "common use" there is similar to the "conventional" in SN 1.25:
Skillful, understanding the world’s conventions,
Loke samaññaṁ kusalo viditvā;
... with "world’s conventions", loke samaññaṁ there, as literally something like "worldly name".
Conventionally, English language grammar has "sentences" which are built using "verbs" and "subjects", and "objects" and so on. There are different ways to use it (i.e. to be expressive or to produce the language) -- for example:
- There's an imperative mood, giving orders: "Cut the grass! Build the house!"
- Or there's a passive voice: "The grass needs to be cut soon."
- FYI I tend to often use an I-message -- because I find that less bossy and argumentative, to say, "I think it's X", instead of, "It is X (and anybody who thinks otherwise is wrong)!"
Pali might not always use explicit words to denote the "subject" in a sentence but I think it might as well, because in Pali the verbs are "conjugated" -- like in Latin for example, the verb amare is "conjugated" as amo, amas, amat, to mean "I love", "you love", or "he or she loves", as different single words -- I don't know if you know a language like that. But I think when you read Pali the "subject" of the sentence may be explicit as a separate word or just implicit (but still implicit), in the conjugation of the verb (which is necessary i.e. conventionally required by the grammar).
In any case I think that, using these languages, it's difficult (or stilted, unconventional) to use the languages "conventionally" without implying that there's a subject and "who" (which person) the subject is.
I think that's maybe less so in some other languages like Chinese -- I don't this know for sure, mind you, I know very little about Chinese -- I think in Chinese you can use an ideogram like "Run" or "Running" without a subject. So you could have a two-word phrase like "run" and "mountain" to say "mountain-running" or "running in the mountain" without implying any particular person who is doing that.
I think there's a form of Buddhist "mindfulness meditation" in English where you're told to think "hearing" when you're hearing something, or "walking" when you're walking. That's maybe similar to the Chinese, i.e. an activity without a subject. It's not conventional dialog though. If we were face to face I could say to you single-words like "grass!" or "hearing!" but that would be kind of odd.
I've definitely seen people (mostly in writing, rarely orally in person) avoid using "first person" (i.e. "I") expression -- for example instead of, "I want X", say, "This person wants X", or even, "She wants X". I think it's good to be sympathetic and permissive to the way people express themselves, but that kind of sentence isn't convention (and other people might find it unusual or uncomfortable). Still it may be what you were asking.
Maybe what's more important or more fundamental isn't grammar but "conceit". I mean this answer:
Also, more about "conceit" on Wikipedia:
Māna (Sanskrit, Pali; Tibetan: nga rgyal) is a Buddhist term that may be translated as "pride", "arrogance", or "conceit". It is defined as an inflated mind that makes whatever is suitable, such as wealth or learning, to be the foundation of pride. It creates the basis for disrespecting others and for the occurrence of suffering.
I think it may be "conceit" that's in evidence, in the quarrel or harsh words ("wounding each other with weapons of the mouth) depicted in the famous parable of the blind men and the elephant in Ud 6.4.
So I think that may be another answer to your question -- i.e. what's more important than whether you use the word "I" conventionally is whether you think automatically, "I'm right and they're wrong" and so on -- even if that's rephrased impersonally like, "such is truth, such is not" etc.
I said,
In any case I think that, using these languages, it's difficult (or stilted, unconventional) to use the languages "conventionally" without implying that there's a subject and "who" (which person) the subject is.
... but that's not true, or not the whole truth -- because you can write "objectively" in English. I think "objective" is when the grammatical subject of the sentence is some kind of object, something other than a person, and other than personal (e.g. "my feelings" are "personal").
Here's an example of objective writing -- the subject here is the Ear (or "an ear"):
An ear is the organ that enables hearing and, in mammals, body balance using the vestibular system. etc., etc., etc.
This implies that you could try to talk about objective or impersonal topics. Here's a page titled Right Speech which quotes nearly a dozen suttas on that topic -- including ones about wholesome and unwholesome subjects of conversation.
I also like this, non-Buddhist discourse -- Bryn Mawr Commencement Address (1986) -- the speaker is an expert skilful with language. It starts with a play on words, then begins to describe "objective" language:
It began to develop when printing made written language common rather than rare, five hundred years ago or so, and with electronic processing and copying it continues to develop and proliferate so powerfully, so dominatingly, that many believe this dialect - the expository and particularly the scientific discourse - is the highest form of language, the true language, of which all other uses of words are primitive vestiges.
And it is indeed an excellent dialect. Newton's Principia was written in it in Latin, and Descartes wrote Latin and French in it, establishing some of its basic vocabulary, and Kant wrote German in it, and Marx, Darwin, Freud, Boas, Foucault - all the great scientists and social thinkers wrote it. It is the language of thought that seeks objectivity.
I do not say it is the language of rational thought. Reason is a faculty far larger than mere objective thought. When either the political or the scientific discourse announces itself as the voice of reason, it is playing God, and should be spanked and stood in the corner. The essential gesture of the father tongue is not reasoning but distancing-making a gap, a space, between the subject or self and the object or other. Enormous energy is generated by that rending, that forcing of a gap between Man and World.
I'll leave you to read the rest if you like. I don't think "objective" language is necessarily better. It has a place or use, it's the language of science, engineering ("The requirement is X, the design is Y"), and probably medicine -- and of a lot of Dhamma. But it's also the language of lies, misunderstandings, half-truths, disputes, bad jokes, and so on, hence my earlier warning against "conceit". It may claim to be "objective" but in fact I think the person is expressing their "view" and to that extent perhaps it's subjective too -- it may be wiser sometimes to phrase as statement as an explicit "I message".
And sometimes I'm not sure it matters -- if a doctor asks "What's the problem?", then whether you answer "There's some pain in the ear" or "My ear hurts", maybe both mean the same thing.
