Wikimedia Bugzilla is closed!

In r16586.

It is not affected for multi-variant wiki. direction always is 'LTR'. Setting $rtl = true; in 
doughter MessagesKk_cn file ignored by MediaWiki. 
  

It's probably the problem of Bug 6100.

*** This bug has been marked as a duplicate of 6100 ***

This bug isn't duplicate 6100. 
Try do following: install wiki with ltr/rtl script variants (currently it is 'kk' only). After that 
click to  قازاق tab. Interface and content will switched to 'kk-cn' (Arabic script), but the 
direction still left-to-right.
I think: probably MediaWiki does not read setting $rtl = true; from MessagesKk_cn.php, and try read 
from main messages file MessagesKk.php only. 
Direction should be RTL when switched to 'kk-cn'. The variable $rtl should be readed 1) from 
current messages file (current variant), 2) if $rtl is not in this file, read from main messages 
file, and 3) default messages file (en). 

Bellow is temporary quick&dirty Javascript workaround for this issue:

if (wgUserLanguage == "kk-cn") 
{
  document.write('<link rel="stylesheet" type="text/css" 
href="'+stylepath+'/common/common_rtl.css">');
  document.write('<link rel="stylesheet" type="text/css" href="'+stylepath+'/'+skin+'/rtl.css">');
}

(Place this statements to MediaWiki:<skin_name>.js)

(In reply to comment #4)
Forgot 'html {direction: rtl;}', so JavaScript should be:
if (wgUserLanguage == "kk-cn") 
{
  document.direction="rtl";
  document.write('<style type="text/css">html {direction: rtl;}</style>');
  document.write('<link rel="stylesheet" type="text/css" 
href="'+stylepath+'/common/common_rtl.css">');
  document.write('<link rel="stylesheet" type="text/css" href="'+stylepath+'/monobook/rtl.css">');
}
And only place is monobook.js (other skins does not work).

MediaWiki has two languages: interface language and content language. The
interface language is the langauge which the user selects: in preference, in
uselang, *or as a variant*. Most messages are used from this language. The
content language is used to get the namespaces and all the other things which
depend on the language of the content. Now, also the page direction is used from
the content language, though it should be used from the interface language.
That's Bug 6100. Here, the interface language is the variant ($wgLang - e.g.
kk-cn), and the content language is the main language ($wgContLang - kk). The
direction is read from the content language (kk), not from the interface
language (kk-cn), and that's the exact problem. If the software reads the
direction from the interface language, it also reads the variant direction, and
therefore it is RTL when using kk-cn. It doesn't for now, but if Bug 6100 will
be fixed, it will.

Remarking as a duplicate.

*** This bug has been marked as a duplicate of 6100 ***