Automatic Reloading
If a Soldier has no ammunition at the end of a turn(alien or human turn doesn't matter),but has still enough TUs to reload it,he'll do that automatically.Since reacton-fire is possible,other actions,like this,may also be possible i guess.
Turning automatically if there's some noise:
If a soldier is looking into the wrong direction,e.g.an alien is showing up behind him,he automatically turn around as a part of reacton-fire,because of the sounds/noise from the alien while comming closer.
At least the soldier has to turn,when he's hit for the first time during that round.