Pasting code into a code block in Confluence looses existing formatting of the code

(I can not reopen the original issue CONF-28966, so I have to clone it)

The issue is still happening with 4.3.7 version we installed over the weekend.

Confluence looses indentation on copy-paste between code blocks.
Steps to reproduce:

1. Create a new document, create two code blocks. Insert indentated text in both of them:

   indentation
     works
       initially

2. Double click in the first code block -> Confluence selects the entire contents of the block.
3. Press Ctrl+C
4. Double click in the second code block -> Confluence selects the entire contents of the block.
5. Press Ctrl+V

Expected result: the two code blocks are now indentical
Actual result: the second code block has the same text, but all of the indentation has been lost (and the font is different as well)

See the screenshot attached to the original bug CONF-28966 as well)

Confluence version: 4.1.9
Browser: Firefox 20
OS: Ubuntu 12.04