Well, this is optional. If you're fine with it, then feel free to leave it. But as somebody that does spend a LOT of time in QMK.... I find that underscores do make it a bit more readable. And I don't know about you, but I've come back to my own code and wondered WTF I was doing. :D So making sure it's readable is a good thing. But it's more important that it's readable TO YOU. 