It doesn't protect me from anything. I just submit the action and if I don't get killed that night I just pretend to be dead...and either 'revive' automatically after 24 hours or whenever I choose to dispel it. I can, however, cast it somebody else - and plan to do just that tonight. I will use it on somebody I think is scum since there's little point using it on myself tonight.
So in regards to the missing kills on the first night I used the ability only one person was targeted. Dupti may have been hit by multiple players...and if I'm not mistaken the flavour text for his death implies as much. On the second night that I used feign death nobody died - so it's very likely actions were blocked somehow by other players.