I'm not the best Nova by any means but I'm decent. She seems like she's the only hero that I play where after the games over, someone from the other team feels compelled to whisper me and trash talk me.
Look I get it. Her whole playstyle is about just popping out of nowhere and 1 shotting you at half health with Snipe. Seems annoying when you're on the receiving end (I've faced plenty of Novas), but really that's her only capability. She has little to no defense. If she misses Snipe, shes a sitting duck other than a well played Decoy, and frankly if you're Nova in a team fight you're often trying to hang out on the edge trying to get a Snipe, and the farther back you are, the harder your shot is.
I also see a lot of people on my team when they are getting killed by Nova often saying "Nova OP bullshit" or something along those lines.
Is she really OP? IMO, I don't think so. But there's no other hero in the game I've seen get people so pissed.