For reference:

http://lists.horde.org/archives/dev/Week-of-Mon-20140203/028488.html

This was NOT a BC break... this was a bug in Ingo 3 not being updated 
to IMP's new 6.x API.

Changes have been made in Git (master):

commit d191add981f82f5f866865fab15463d25a0e1f9f
Author: Jan Schneider <jan@horde.org>
Date:   Mon Feb 3 20:24:56 2014 +0100

     [jan] Fix behavior of 'utf' parameter (Bug #12937).

     Conflicts:
             ingo/docs/CHANGES
             ingo/package.xml

  ingo/docs/CHANGES |    5 +++--
  ingo/package.xml  |    3 ++-
  2 files changed, 5 insertions(+), 3 deletions(-)

http://git.horde.org/horde-git/-/commit/d191add981f82f5f866865fab15463d25a0e1f9f

Changes have been made in Git (master):

commit 5b49c5c0b64c87ded0410b01072b57fbbbfa8674
Author: Jan Schneider <jan@horde.org>
Date:   Mon Feb 3 20:21:09 2014 +0100

     The mail/mailboxList returns UTF-8 encoded folder names now (Bug #12937).

     When did this change? This is clearly a BC break.

  ingo/lib/Script/Sieve/Action/Fileinto.php |    4 ++--
  1 files changed, 2 insertions(+), 2 deletions(-)

http://git.horde.org/horde-git/-/commit/5b49c5c0b64c87ded0410b01072b57fbbbfa8674

Changes have been made in Git (FRAMEWORK_5_1):

commit b04e1e1984f48daa9d16b30a425e0e0d5063b9d0
Author: Jan Schneider <jan@horde.org>
Date:   Mon Feb 3 20:24:56 2014 +0100

     [jan] Fix behavior of 'utf' parameter (Bug #12937).

  ingo/docs/CHANGES |    1 +
  ingo/package.xml  |    6 ++++--
  2 files changed, 5 insertions(+), 2 deletions(-)

http://git.horde.org/horde-git/-/commit/b04e1e1984f48daa9d16b30a425e0e0d5063b9d0

Changes have been made in Git (FRAMEWORK_5_1):

commit cecc0d08813e2bdb2cf8562af27fcc3f7de01040
Author: Jan Schneider <jan@horde.org>
Date:   Mon Feb 3 20:21:09 2014 +0100

     The mail/mailboxList returns UTF-8 encoded folder names now (Bug #12937).

     When did this change? This is clearly a BC break.

  ingo/lib/Script/Sieve/Action/Fileinto.php |    4 ++--
  1 files changed, 2 insertions(+), 2 deletions(-)

http://git.horde.org/horde-git/-/commit/cecc0d08813e2bdb2cf8562af27fcc3f7de01040

The 'utf8' parameter, as described in the backends.php, should enable 
the UTF-8 encoding for folder names. The code that uses the parameter 
is found in lib/Script/Sieve/Action/Fileinto.php, and looks like

if (!empty($vars['utf8'])) {
    $this->_vars['folder'] = 
Horde_String::convertCharset($this->_vars['folder'], 'UTF7-IMAP', 
'UTF-8');
}

However, it seems that the folder name is already coded as UTF-8 when 
this code is reached, with the result that each non-ACSII character is 
turned into a sequence like '??'.

On the other hand, if the 'utf8' parameter is false or not defined, 
UTF-8 characters in mailboxes work fine.'

Thus, both the description and the code seems to come from a time when 
folder names were stored encoded as IMAP-UTF-7. Unless this can still 
be true, the parameter should be removed and the examples in 
backends.php should be updated.

Thanks
Arne Nordmark