this is no way a comparison,.. Soul is just describing his team members,
“a groove between Q and Langston Hugh means that Q is not really that deep or poetic,.. so he is typical opposite of Langston Hughes,.. Kendrick is a spitter thus the acid tablet reference,.

I honestly feel “making sure my punctuation curve” is to imply he’s trying to ask, to not tell this story in a biased way, the curve implying a question mark. He is an honest actor, which is something you can’t know, he is making sure he’s asking questions in his punctuation and thusly in his communication, and that he is at least true to the facts and never lies in these letters.

I think I have a neat addition for the link between “margin” and “proof”… Pierre de Fermat. Pierre de Fermat was a famous 16th Century Mathematician who made early contributions to infinitesimal calculus. (maybe even linking into the word “curve” mentioned earlier, since calculus has a lot to do with curves!) But back to the point, Fermat was probably most famous for coming up with “Fermat’s Last Theorem”, which states that no three positive integers a, b, and c can satisfy the equation an + bn = cn for any integer value of n greater than two. He apparently conjectured a proof for the theorem at around 1637, and wrote in the margin of his copy of a mathematical textbook called Arithmetica (where the theorem was written) claiming that “he had a proof that was too large to fit in the margin”. This problem baffled mathematicians for literally hundreds of years (if you want to learn more about it, there’s a book which has been released which has the same title) and no successful proof was given up until 1995 (by a clearly incredible mathematician, Andrew Wiles).
Linking this to Kendrick’s genius, the line could be saying that the metaphor “living my life in the margin” clearly has to do with Kendrick’s incredibly eventful life, with the “proof” of which being far too big to fit in any sort of margin and/or a line in a song/a verse/a whole track/an album to be fully appreciated. Incredible wordplay.

We’ve established that Kendrick is implying that he doesn’t stop when he writes ‘'make sure my puctuation curves.’‘ But he could also be making a double entendre.
If we suppose that Kendrick was using the term ’‘punctuation’‘ in the broadest sense of the term, we could interpret this phrase as Kendrick telling his audience he throws wordplay out that he intends to ’‘curve’‘ or confuse the listeners, to get them thinking. To continue with the baseball metaphor of a curveball, Kendrick is ’‘making sure’‘ he makes it hard for the audience to ’‘keep their eyes on the ball’‘ the same way a curveball is hard to hit. This is essentially what a double entendre does by making your brain have to choose between equally likely interpretations.

By this reasoning, what K most likely means by ‘'every letter here’s true" is merely that his continual effort is demonstrated by the next metaphor.
In the next metaphor, Kendrick says he “lives his life in the margins.” At some level he is saying that his life IS poetry (or rap, w/e), His raps are pages straight out of the book of his life.
He ends the bar saying that the whole structure of this bar, as nuanced as it is, is proof of his dedication to his art.

In my opinion, Kendrick is pointing to the likely fact that this bar is too complicated to be created by an amateur rapper. It’s not a simple metaphor or simle it’s also a double entendre. It is carefully constructed and more like poetry than rap. Poets are known to be more symbolic, metaphorical, etc with their poems than rappers. '

This could also be referring to Fermat’s Last Theorem, in which he claimed that he had a solution to a problem, but it was too large to fit into the margin.

Fermat's Last Theorem - Wikipedia — Wikipedia