@ian GSF2 is RAMPANT on AO3. The comment culture there (unlike FFN, where comments are called "reviews") is such that any criticism, no matter how polite or constructive, is considered taboo, rude, and offensive unless the author explicitly invites it.
Anything less favourable than "omg i love this story this is the best thing ever omg" is met with (ironically, considering GSF1 is also quite prevalent there for the most part) uninhibited vitriol telling the critic to go fuck themselves and die and stop being so negative and they're probably an "anti" anyway.
And despite this violent form of GSF2, GSF1 dominates the site as well, because any attempt to discuss trolls, rampant racism and misogyny, etc. on the site is also met with accusations of being an "anti", wanting "censorship", and whatnot.