Like you, I approach fest stories as gifts. I think leaving negative feedback to an anonymous gift fic closely mirrors this scenario:
In a spectacular moment of OOCness, the cast of HP are all celebrating Christmas together, and they're just in the midst of opening gifts.
Draco: omg a pony! Pansy, you shouldn't have! Kreacher: That's the ugliest pony I've ever seen. Draco Malfoy deserves a better pony. Look at it! It's black. It should at least have a silver mane. Harry: Wow, Ginny, thanks for the nose hair trimmer! That'll, uh, really come in handy. Kreacher: Ridiculous. The filthy half-blood has received a gift that is completely useless, since he doesn't even have any nose hair, at least not if fandom is to be believed... Dumbledore (conveniently back from the dead): Socks! I love socks! Who gave me socks? Was it you, Minerva? omg I love you. Gimmie some sugar. Kreacher: Socks are for fags. etc.
no subject
In a spectacular moment of OOCness, the cast of HP are all celebrating Christmas together, and they're just in the midst of opening gifts.
Draco: omg a pony! Pansy, you shouldn't have!
Kreacher: That's the ugliest pony I've ever seen. Draco Malfoy deserves a better pony. Look at it! It's black. It should at least have a silver mane.
Harry: Wow, Ginny, thanks for the nose hair trimmer! That'll, uh, really come in handy.
Kreacher: Ridiculous. The filthy half-blood has received a gift that is completely useless, since he doesn't even have any nose hair, at least not if fandom is to be believed...
Dumbledore (conveniently back from the dead): Socks! I love socks! Who gave me socks? Was it you, Minerva? omg I love you. Gimmie some sugar.
Kreacher: Socks are for fags.
etc.