I've been running dovecot for a while now. I've got 1.0alpha5 running on a Slackware linux 10.2 system (i386). My system is using mbox format which means you can't have folders that contain both folders and messages.
What I'm seeing is that removing folders doesn't always work. From what I can tell, it only affects folders that contain folders. Dovecot doesn't remove the directory from the server when the folder is removed which means it just keeps coming back.
It's easy to duplicate this. Just create a folder that is allowed to contain folders only. You will see a directory created on the server. Then remove the folder. The directory will still be on the server, even if it is empty (i.e. no dovecot index files in it).
Of course, most people create folders and never delete them, but occasionally it's useful to do so.
For the record, removing folders that contain messages (mbox files) works.
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