Confluence page render in Chinese Character when Encoding change to UTF-16

Problem

When the administrator change the character encoding from UTF-8 to UTF-16 at the general configuration page. The confluence page will then render in chinese character.

In confluence log you will only see :

2014-10-15 05:26:03.000265500 2014-10-15 05:26:02,998 WARN [TP-Processor32] [atlassian.confluence.themes.DefaultThemeManager] extractTheme Unable to find configured theme module: com.atlassian.studio.confluence:studio
2014-10-15 05:26:03.000267500  -- url: /wiki/admin/flyingpdf/configurepdflanguagesupport.action | userName: sysadmin

To verify this is the problem run in the database:

SELECT BANDANAVALUE FROM BANDANA where BANDANAKEY = 'atlassian.confluence.settings';

if it returns a different value of UTF-8 in the result, then it is affected.

Steps to reproduce:

1. Set up a new Confluence
2. Go under the Administrator Panel > General Configuration > Formatting and International Settings and change Encoding field from UTF-8 to UTF-16.

Expected Result:
Confluence doesn't allow the change
Actual Result:
Confluence becomes unusable, styles are broken and administration sections are locked.
Can't be reverted back unless a DB change is done.

Workaround

1. Check on database to confirm whether it is in UTF-16

   select * from bandana where bandanakey = 'atlassian.confluence.settings';
   

2. Update the database to UTF-8

   update bandana set bandanavalue = replace(bandanavalue, '<defaultEncoding>UTF-16</defaultEncoding>', '<defaultEncoding>UTF-8</defaultEncoding>') where bandanakey = 'atlassian.confluence.settings';
   

There is a similar bug ticket CONF-7883 created long ago but it is obsolete.

I believe this is still happening on all instance as it is replicable at my dev instance.