Silangan this made me laugh. proofread? I doubt the guys in ffn.net even know what the word edit means. They're even more amateurish than the original authors here, and that's saying something.
As for ao3, the level of professionalism the is somewhat higher so yes, they do proofread, problem being 99% of content on that site tends to be erotica in one form or another.
Of course, this is just me talking about generalities, I don't deny there are some. Very good stuff there, works that are of even better quality than anything webnovel currently bad to offer. No Chinese stuff though, and it's all fandom based, so you'd be hardpressed to find good original novels.