I've used this before but only for fun, lol. In serious use cases, it shouldn't cause any issues during runtime and should work like any other character.
My only potential issue for not using this is because of the writing and searching process, and that's all. I search emojis on Google and it takes more time writing emojis since I use a desktop keyboard (even with Windows emoji), which I think is a different case if I used a smartphone's virtual keyboard. Writing 🔫 takes more steps than typing weapon
, you see.
Furthermore, since it's a picture that 'could' show differently depending on the device or platform, there's a chance it's a different emoji than what you could've expected, for example: inconsistencies in used emojis. It could lead to an organization issue.
Nevertheless, I see the benefits of this, especially with guides. Emojis shouldn't cause any issues with JavaScript and other languages, hence Construct 3 shouldn't either, even advanced minification shouldn't have any issues with this.