Promoting the idea of using discord for clans seems flawed, as you are moving traffic away from the games official forums to an independant server that often loses all link back to toribash, other than the occaisional comment or channel just for it. Promoting activity on the forums and not discord is promoting activity in the game and for the game, so in my eyes everything discord related shouldn't be officially supported.
However, what I would like to see is some in-game requirement for clans to become official, probably not in the form of wars complete but simple users in game and averaging a certain threshold of games per day. I think the square brackets are enough of an ingame reward, as despite being subtle, they are noticed by the vast majority of people and often well respected. Maybe an addition such as 3D armbands, however that would likely just get confusing and not worth the time to create.