Editing a Section discards Escape Character

If a page contains a percentage character % that is escaped by a tilde, the tilde gets removed each time you edit a section
of the document. Editing the whole document does not show the effect.

I created a test-case on the playground: http://playground.xwiki.org/xwiki/bin/view/Sandbox/EscpapeTestcase
The page contains a (~%), when clicking on the section edit box, the tilde gets removed and the whole page content
is no longer rendered properly because (% is a special sequence for xwiki