Out of curiosity, why do you consider folders to be sane, and labels not?
To me I always found labels to be the exact same as a folder, but not bound to a single instance. Ie, it is everything a folder has, and more. What am I missing?
Labels are one of the very few things I miss when I switched from Google Apps to Fastmail, but labels sometimes do not work well with IMAP. Google Mail exposes labels as IMAP folders, but in an IMAP client, you will have identical messages in different folders. And since traditional IMAP clients are not really equipped to deal with them, label management gets annoying.
To me I always found labels to be the exact same as a folder, but not bound to a single instance. Ie, it is everything a folder has, and more. What am I missing?