Yeah, I considered the circles, but for folks with red-green color blindness, that difference in shape is essential.

And as for 2-char-width, normally I'd agree, but I could have used ✓× with manually set font color, and well, I didn't.
The emojis are preferable to me, because they stand out from normal text. And they do that, because they are bigger and because their bigger size allows plastic design elements...