It's the worst thing to happen to this board, and dare I say this whole website.
Before discord you had a hivemind of faggots all posting dumbass bullshit but at least it was a hivemind of faggots all posting dumbass bullshit at a moderate enough pace that the particularly shitty posts could be filtered out and the rest of the threads would still contain decent posts. Now, with discord added to the mix, you add a kind of meta hivemind of faggots posting dumbass shit on top of the already steaming pile of shit. Worse still, discord encourages a sense of unity via the creation of groups. What you are left with is a bunch of faggots posting awful threads with another layer of faggots posting awful threads who are engaging in war with opposing groups of faggots posting dumbass threads by planning and coordinating massive waves of stale memes in the hopes that their group will post more of their stale memes than the other group and thus claim their dominance. Now even when you filter out threads, you will still be left with shitty threads until there is nothing left. Discord is a disease.