The only way to verify that they own the asset was the key icon left by comment or review, e-mails don’t allow that; anyone can edit/photoshop a receipt. Anyone that pirates/steals your asset can still e-mail you.
I always gave them the option to leave either comment or rating and never forced to rate it good or bad (Someone rating 1 star will still get them verified). So, how is it ‘fake’?
All this does is get people that are fine with the asset(The silent majority) to communicate and voice their opinions that would of otherwise stayed silent.