[Cthulhu_]

It should always be taken with a grain of salt; I guess you can make sweeping statements like "positive/negative tone", but you should be careful attributing exact meanings to it. I mean to some, an eggplant is an eggplant, to others it's a penis. There will be community specific meanings attributed to certain emoji, often unspoken or even unaware.

[icebraining]

Just like with words, or colors, or mostly any kind of element of communication.