Unmarked juxtaposition means "about" ?!Correct: mi toki jan. -- I talked about people
It's tricky to deal with this because who's to say what is wrong and what is right, who is the real language designer for toki pona--is it jan Pije or jan Sonja or is it a living language and the total corpus actually reflects the rules better than the putative designers?, etc.
That said, jan Pije is wrong. Unless this is a predicative sentence, everything following the verb until you hit a preposition is part of the verb phrase. So either we have the oblique being incorporated into the verb, (I people-talked, I gossiped) or this is just missing an "e" or a suitable prepostion. If we have noun incorporation into the verb-- or marking some obliques with only juxtaposition, then "e" and prep dropping becomes quite alright in just about any situation-- I'm seeing people continue to use "e" and prepositions-- I'm not seeing the corpus a lot of e dropping or prep dropping-- at least nothing that looks intentional. Beginners tend to drop e, people who've been writing for a while don't.
mi toki (e nimi mute) tawa jan pona mi lon jan.
I gave a speech (talked) to my friend about the people.
Like most obliques that aren't concerned with spatial relationships, toki pona is impoverished in options that don't require some sort of arbitrary metaphor.
If we use juxtaposition, we get an adverbial reading
mi toki jan (e nimi mute) tawa jan pona mi.
I humanly (like a human) spoke some words to my friend about people. Something about the talking had a salient quality of humans-- so which ones? Probably something abou how those humans speak.
If we did want to have noun incorporation into verbs, it would make more sense to use "pi", because "pi" introduces a noun (as opposed to a modifier) and prevents the adverbial reading.
mi toki pi jan(mute) (e nimi mute) tawa jan pona mi.
We have more evidence that noun incorporation is a innovation-- the is no strong reason to have 2 words after the pi in a verb phrase, which breaks the rule that the last pi in a pi phrase be followed by 2 words.
Noun incorporation could be useful in multi "li" phrases, e.g.
jan pali suli pi ma Mewika li pali pi pan li moku pi moku li pona e supa moku mi. (Yes this could be 3 sentences, but with anaphora in tp being as weak as it is, I'd rather a strong subject and not have to repeat it 3 times)
Anyhow, it would be an innovation. I'm not opposed to innovations, but they just need to be done consciously.
This page also has "li pi", which is something that almost no one uses-- just because it's in the language spec doesn't mean it's right and the collective community of toki pona users appeared to have considered 'li pi" as wrong.
Unmarked juxtaposition for tawa has better grounding, as it turns out several natural languages do predicates that imply motion. Unmarked obliques just because we're not sure what a suitable preposition would be is just wrong.