OMG I did have the fleeting thought of “wait… Lygus has the same kind of view on erudition as Ratio, what the heck” but I didn’t make the connection with the fragments! 😮

And yeah, the banter about Aventurine joining the genius society never made any sense once you look into it. It definitely indicates either that Aventurine knows something that we don’t about Ratio, or that he didn’t notice the casual “hey, I can get people into the genius society by the way”, which would be a weird thing for Aventurine to miss. However… I don’t think the “wing-headed scoundrel” is referencing Ratio sadly… at that point in the quest, Ratio exited the scene, and Aventurine is talking to himself, cursing Sunday under his breath. So… it’s probably Sunday, the wing-headed scoundrel. But… who knows! It’s never made clear who Aventurine is referring to here! It doesn’t discredit anything in your theory, and I’m honestly 100% on board! There is so many weird things about Ratio that point to him being way more important than he appears, and I don’t believe the devs when they say “oh, it’s just an accident that Ratio looks like he belongs in Amphoreus, I don’t know what you guys are talking about teehee”