Greetings.
Thanks to Jelmer Vernooij, who has just uploaded version 2.2.16 for Debian unstable, I can confirm that this bug may still be reproduced in version 2.2.16, so it has *not* been fixed yet.
Several months ago I was told "I can't reproduce it in dovecot hg", or something like that. Well, having this fixed in hg does not help very much if the bug is still present in the latest released version (2.2.16).
Would anyone here please tell which commit exactly fixed this issue?
If it's not fixed yet, I would love to provide a patch, but I'm not a programmer myself.
However, I provided a very precise and detailed explanation about how to reproduce this bug, which you will still find in the Debian BTS:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=776094
Really, it should not be so much difficult to reproduce it. Try on a Debian 8 system. I'm sure that if you follow the steps exactly as I described, you will find the problem the same way as I did.
Thanks.