Remove or fix privacy UI that may mislead users
The latest version (based on Fennec 45.4.0) seems to use permanent private browsing mode. In this mode, the only way to clear browser state is to use the "Quit" menu option or swipe the app off the recent apps list.
Currently, the "Clear private data" option merely appears to work (it even displays the "Private data cleared" toast), but does not actually do anything. Contrary to expectations, closing all private tabs does not clear private browsing state. State leaks between "normal" and private browsing tabs.
Try http://browserspy.dk/cookie.php for a demonstration. (note that, to see the cookie it placed, you should reload the page once after the first load)
On desktop FF, permanent private browsing mode means that normal tabs are private, and there is no separate private browsing mode. The "Clear private data" option is completely inaccessible.
Orfox should adapt its UI to match the actual privacy model, or at least change it so as to not mislead users.