kinda pissing me off seeing people saying that david production needs to "correct" arakis "mistake" and invent a new scene to show off johnnys birthmark. have you considered that sometimes when an author chooses not to show you something its because you, the reader, are not supposed to see it.
so the big theme of jojo is the familial legacy, right, and the birthmark is shorthand for that. jonathan is actually never pictured with it either: it gets retconned in during pt3 as a visual metaphor for the joestar familys shared lineage/"destiny" that persists even after jonathans descendants (and remains) are scattered across multiple continents. joseph in nyc, jotaro in japan, dio in cairo, giorno in italy, and eventually even pucci in florida. the "golden spirit" that jonathan inherited from his own father(/mother) gets passed around by both natural and unnatural means.
the other thing you might notice johnny and jonathan have in common design-wise is the way that they dress: rather patriotically. jonathan wears the union jack, johnny wears the stars and stripes. none of the other jojo characters have their national identity really incorporated into their visual branding the way those two do.
so what does that have to do with the birthmark (or lack thereof)? because the family is a microcosm of the nation, obviously. in sbr #87, a young funny valentine is told by his stepfather-to-be that "'patriotism' is the most beautiful 'virtue' in this world. even animals risk their lives for the sake of their children, but risking one's life for pride in their country and thinking of it as an extension of protecting one's family is only a 'nobility of humanity'…"
jonathan has a strong sense of fealty to both his family as well as his nation; johnny, by contrast, has disowned both by the time his journey comes to an end. in his fight with valentine, johnny confronts the pretense that defense of one's own family/nation is an inherent good. he acknowledges, in fact, that under such a moral framework, valentine, animated by respect for his late father and devotion to his country, might be "righteous"; and that johnny himself, by opposing him, is "evil". as readers, we can easily make our own moral assessment of valentines goals, and the measures he takes to see them through - but valentines patriotism and ambitions for his country are genuine, and he gives his own life for that end because he believes in the inherent righteousness of his cause. thats why you never see the star that may or may not be on johnnys back, but araki makes sure you do see the ones that are on valentines
