I also find that stuff distracting in slack, but I think that's because I'm trying to stay on top of "work stuff". I don't think it'd be so distracting if I was just hanging with friends or something.
I dunno. I haven't tried it. For me, when I'm in a social situation (virtual or in person), I'm there for the people and want to focus on them, not some animated emoji. I can do those on my own.