Is there a way to identify "fake flacs"

While i was walking through Nicotine+, i discovered the Interests section. It is a very cool function. On the most dislikeds tags, there was "Fake flacs" and "uploaders who convert their youtube mp3s to flacs". Then my mind blew up... People actually do this!

So, is there a way to identify a "fake flac", or just download from trusted sources?