Sup's inbox-mode appears to fail to save thread state accurately for me, such 
that a quit and re-open of sup or even a @ on the inbox will nearly always show 
some threads that should have been archived.

I haven't found why this only affects some threads.

My normal workflow:
. open a thread (now it loses it's :unread tag)
. stuff
. x out back to the index
. a to archive (now it loses its :inbox tag)
. repeat
. $ to save the inbox state

At this point if I close and re-open sup, or if I @ to refresh the inbox view, 
there is a chance that the message(s) I just operated on will re-appear in the 
inbox as unread.

It also seems to happen if I N and a messages from within the inbox-mode.