I did a couple tests and the shift-tab and tab work pretty much as expected. There's a small quirk for a single-line edit:

* place cursor on beginning of line
* tab forward
--> the text indents as expected
* shift-tab
--> the entire line is highlighted
--> the cursor now appears beneath the line
--> subsequent typing however affects the highlighted line

For the single-line case, it would be cleaner to have it stay on the same line without highlighting.

This is OSX 10.9, python 2.7.6+ and 3.4.rc1+