While mutt has
set sort = threads to show threaded, "conversation" style messages, it doesn't display one's own replies in the threads. Instead, you have to change to the Sent folder to see your own messages. Is there any way to display one's own replies where they belong inside threads?
Edit: I found
notmuch-mutt has some of the behavior I'm looking for. It defines a macro that looks at message-ids and can create a virtual folder to show an entire threaded conversation regardless of where each message lives. Out of the box it only works on search results. I'll have to do some more digging to figure out how it works and see if the same behavior can't be applied to regular mailboxes.