When the cursor is in the HTML editor text entry area, you cannot press Shift-Tab to get to the previous tab stop.

To reproduce:
1) Go to a forum 'Reply' page (for example; any html editor will do)
2) Click on the message subject text field so that the focus is in there.
3) Press Tab repeatedly. You will see focus move through all the buttons in the HTML editor. Finally it will arrive at the text entry area part of the editor.
4) Press Shift-Tab.

Expected behaviour: Focus moves to the previous tabbable control (the triangle dropdown next to the spell check button).

Actual behaviour: Focus does not move, but remains in the editor text entry part.

Note that it IS possible to continue tabbing forwards to controls that follow the area. Also Shift+Tab works everywhere else on the page, including within the HTML editor buttons. Only tabbing backwards from the main text input area does not work.