Absolutely horrifying, perhaps even more so after the quantiles were reworked:

library(ggplot2)
ggplot(mpg, aes(drv, displ, fill = factor(year))) +
 geom_violin(position = position_dodge2())

^{Created on 2025年09月29日 with reprex v2.1.1}

@karawoo had described this many moons ago https://youtu.be/UGAuXyxdrvA?si=q9GH8ety6Xj1ak5t&t=986, but I couldn't find a related issue that kept this on the radar. This issue is that blip.

I think fundamentally position_dodge2() doesn't know the relation between rows and groups. For many geoms, 1 row is one group, like geom_boxplot(), but in others there is a many-to-one relationship, like geom_violin() or perhaps geom_dotplot(). I think the meat of the issue is how we can communicate this information between geom and position. The implementation at the position level worries me less.