Discord is a blight upon humanity.
Giving autistic children with niche interests the ability to talk to autistic adults (and as with this case, other autistic children) about said niche interests is probably the worst idea in the entirety of human civilization. These days we have kids doing and talking about shit they absolutely should not be doing or talking about, and adults who are easily able to prey on these stupid children.
That said, this particular case doesn't seem too bad. A 15 year old offhandedly making a few dirty jokes in a chatroom with a 10 year old is pretty far from ”grooming”.
But kids that young REALLY shouldn’t really be on Discord with random anonymous people in the first place. Especially when they’re in chat rooms regarding weeb games.