I think that's probably close to right. I had a couple experiences where I made meme comments on people's memes and some people seemed like they were taking it as if I was making fun of them, when I hadn't meant it to come across like that.
So I think that's probably why I started doing it - just to get that little bit of extra grace where if the person thought I was being mean, they would see the smiley face next to it, and rethink that possibility.
Also, I like smiley faces.