This bug experienced in 1.8.3 and all 1.9 versions.
articles or wiki page EVEN WHEN using the code plugin or
when enclosing it with ~np~ ~/np~. When the article is
set to "allow html" the code isn't stripped but it displays
as if it has been stripped. If the article is set to "not
allow html", then the code gets stripped inside the
article too (not only on display).
The attached screenshot displays some XML code. On
the left the original code in the edit article window
(with "allow html" on). On the right, the way the same
code is displayed when viewing the article (also
with "allow html" on).