Because, unless someone wrote a reply solely to you and went out of their way to reveal Akira's name, we're on a thread to talk about the game. Spoilers are going to fly everywhere you look. Now, if it was a reply to you, I'm pretty sure it wasn't made out of malice but rather out of habit since, well, it is his name. A substantial amount of people call him Akira ever since because that's his name. It's much easier to remember to hide knowledge of a thing that happened than it is to remind yourself you can't call someone by their name all of a sudden.
Not specific to you now, but since the topic was brought up, I don't personally think anyone should go out of their way to hide spoilers, nor should it be an expectation. The community tends to do a good job of using tags right after an update to talk about the update, but other than that we mostly talk to other regulars here, and it'd be pointless to keep using spoilers to talk to people that all know what the spoilers are.
The situation of the thread is one where, even though we welcome newcomers, it's kind of showing up to a book discussion club when you haven't read the book. If someone is that adamant about not being spoiled, the only way is reading it before showing up - because it is going to happen no matter how much people might try to protect you.
Also I've been spoiling that Himawari's name is Ami forever, and even though Selebus hasn't proven me right yet, you all know I am.