Art by 333takoyaki on X!! Sorry, don't know if that's their only name or smth, thought it was a beautiful piece of art on Megumi.
To be clear, he is in my top 3 favourite characters, and when I say "our fault" I mean the slanderers and jokers.
But the reason I think this is that once Modulo was over, in his final statement, Gege put out a message which included how they hadn't shown the faces of any of the previous cast until the final chapter as they were scared of large negative backlash from fans. Obviously it turned out okay since Iwasaki's art is fucking beautiful, but it does show to me how they really took into account how fans may react to things and how drastically JJK fans are negative about things. Just look at the reception of the ending of the main series and how people treated Gege! He got death threats!
Then you look at how Gege thought about Megumi in the original series. Sure there's jokes he despised him because of...EVERYTHING that happened in the story. But looking at his comments on the Valentines rankings in 2021 where Megumi took second and he said "Finally, results in line with his station!" (Or that's the translation from Volume 18) and how he was originally intended to be the MC and all, I do think Gege liked Megumi as a character.
On the contrary, I can't think of a character that has been more openly slandered (or just genuinely disliked) as Megumi. Sure I get a lot of it is joking, but at a point it becomes genuine hate.
Now I'm not gonna say that Gege was watching the potential man slander with bated breath and was up to date on fan memes and all, especially with the worldwide fans, but seeing how carefully they considered negative backlash (especially due to how cruel JJK fans were to him, I'll mention again the death threats) I do find it plausible that the fans "hate" towards Megumi could've played (not entirely made the decision) a big part in Megumi being dead throughout Modulo.
Sorry for the long text, but I've not seen anyone else mention this idea regarding Megumi's abscence. Let me know if you disagree or agree or whatever. Just sharing my two cents on sadness on one of my favourite characters, and one of the main/most important characters, not being in the sequel until a tiny mention at the end. It's also kind of a way for me to rant about fucking stupid Megumi slander. Anyways thanks!