With the game mechanics Minecraft has today, and the Warden being known for glowing in the dark, I dont see why Glowing Costumes aren’t a thing yet-
The Glowing effect would look nice in Gamemode’s that have Night set by default, I don’t see why this couldn’t work in Hub / Arcade too when it gets Dark, this would also give Hive a reason to update existing costumes to have a glow effect (depends on the costume) if not then it would be cool idea for the next Halloween event to be a costume with this effect.