I have found two bugs related to tab completion.

1. Setting “tab_completion”: false in User File Preferences does NOTHING.
   You have to modify the Default ones and restart ST2.

2. Shift + Tab does not work as expected when tab_completion is really OFF.
   It just inserts a regular tab nor untabs the line.

Hope it’s not hard for you to fix John.

P.D: Sry about those bug-tweets