In Sword Art Offline 2 episode 7, Asuna comments that Yuuki not only is a rare tomboy female player but also talks like a boy.
Now, I watched the English dub and didn't pick that up so I guess it is something you'd only hear when you watch the sub with Japanese audio, but even in Sword Art Offline which was never dubbed (only subbed with Japanese audio), I didn't get an impression that Yuuki was talking like a boy.
So how is it that Yuuki talks like a boy?