WebGL supports antialiasing, but it has a big performance overhead and isn't necessary for smooth edges, so we have it permanently disabled in C2 and C3. The reason the crop tool leaves a 1px transparent border is to get the smooth-edges appearance using linear sampling only, since it smoothly blends with an extra pixel of transparency at the edges, rather than having a hard edge. This is much more efficient than running a full antialiasing engine and looks pretty much the same. So enabling antialiasing will only cause a major slow down with no real visual quality improvement.