Only thing I'm sure could be better is it needs higher-contrast text still, a darker background for the dark theme might do it. Get somebody with old eyes in there, low-contrast text is great for advertising copy and other novelty/attention-seeking contexts but it sucks for older eyes.
Haven't found how to lose the avatar pics, when thread-reading, they suck up so much space you can't see more than three posts in a conversation. ffs I could see more on a 1960's 3270 with a 24×80 text screen. If you really can't turn them off I'd say that's going to be my vote for worst feature ever.
Everything else looks like it's there just a matter of getting used to the new setup. I like the expando toggles, could wish for checkbox selections for selective "mark read" ops and such but I know that's soaring pretty high up there in first-world-problems territory.