I could see some use in being able to flip between date-sorted and thread-sorted. For example you just want to see the latest messages and then use a command to see the previous messages in the thread. That's sort of like how gmail works.
I certainly would not object to just having a config option as a first pass.
Would be nice to not have to restart aerc after closing the laptop lid.
This could be quite nice for following along on a long mailing list discussion.
When I quickly scroll through the folder list the UI can be quite slow. I suspect it's because the folders are large and aerc is trying to fetch messages lists, although I have no way to prove it.
It'd be nice if going to the next folder had an immediate response.