That would have to be litigated in court, and the easiest and cheapest way to avoid litigation is to do what all platforms currently do: make sure the person using their system is who they say they are via face scans and ID checks.

As a developer, that is not the kind of liability I want to take on when I can just plug ID.me, or whatever, into my app and not worry if someone writes "im 12 lol" in a comment on my platform.