Personally, I think the use of emojis in subject lines should be determined by 1) the voice and tone of the person/company you are speaking on behalf of, 2) the audience you are speaking to and 3) based on data, preferably determined through A/B test results. For example:
InkAddict often uses emojis that feel relevant as well. Their brand foundation is built on reflecting alternative, tattoo culture and community.
Here at Alliance Health, we haven't used emojis in our subject lines yet (but it's something we should test!). We are beginning to introduce a more energy-infused and accessible tone across our communications and emojis feel they may fit within that voice. However, because our audience demographic consists mainly of leads over the age of 45 it may not connect well with them. This is where our testing will come into play! We will have to keep the community updated on what kind of results we see.
Ryan Murano great comments and insights. Definitely agreed that the audience is one to take into consideration. However, I wouldn't exclude the 45+ age group I can honestly say that my wife is an emoji queen in her texts! So keep testing away and see what works and who responds.
Trent! Small world! That was my ClearVoice post you came across.
I've been testing out emojis for my main employer, Kuali, and have seen strong results. We sell to higher-education professionals, which tend to be more sophisticated... but even with that they have still responded well.
For example, in one of the subject lines, when we were soliciting event attendees to meet with us at a conference, we saw 40% more opens by using a "sun" emoji: