User blog comment:XGlass Reflection/Ch. 54 Review~ Erwin of the Rebellion/@comment-76.208.146.99-20140220002635/@comment-179280-20140220222120

@Misk I said the anime handled that part poorly because it focused too much on Annie, and that forcibly meant they had to draw her like a default, androginous, unidentifiable character not to spoil the audience. That has lead many anime-only fans to create some really wild theories about who could "the killer" be, even throwing Marco around as a possible zombie traitor (yes, that wild). In the manga we don't have that problem, because you never see her face or her clothing. All we see is someone in the distance wearing the Survey Corps cloak, maneuvering and catching Gunther unprepared. We later see how that person transforms into the Female Titan, which turns out to be Annie.

@ That's what is cool about opinions, because we all have different ones. In my case, I think that the anime ending was really stupid and unnecesary. But well, that's just me.