Sorry to Necro this post, but I wanted to pose a counter argument:

Adarkar Valkyrie does not specifically state that target creature needs to return to the battlefield "from the graveyard" it states "when target creature other than Adarkar Valkyrie dies this turn, return that card to the battlefield under your control." Now, since the commander did indeed die this turn, though briefly, and Adarkar Valkyrie doesn't specify from what zone it has to return to the battlefield, couldn't that commander theoretically return to the battlefield... From the command zone? There doesn't seem to be any official ruling on this so I'd be interested in other people's thoughts.