That's a hard problem! I don't know. But when we select colleagues we build trust before we let them in the building by interviewing them, looking at their work, checking their references. So maybe there's some sort of analogous process that isn't just "here's a big PR, look at it" that would be useful? If there was such a process, maybe that kid could go through it and become trusted.

EDIT: from Github's selfish perspective, this would gatekeep their CI load. I assume (I have no idea, it's just a guess) that mostly serving source code and handling commits is not primarily the scale problem. Instead (again just guessing) probably the vast majority of the compute load due to PRs is running all the CI checks. Nontrivial projects can spawn a hell of a lot of compute per PR, and on every subsequent commit pushed while the PR is open.