Think of it like a billboard at a local college. The college puts a billboard up for students to make community announcements. The college never uses it. Then Adam writes something defamatory and false about Betsy. Betsy is upset and sues Adam and the college. A court would allow the lawsuit to proceed against Adam, but not the college because they just provided the platform and had nothing to do with the comments.

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But the college would be liable if college staff erased Adam’s comments and changed them to something else. If Adam was originally saying something mild about Betsy, and instead a college staffer changed it to something defamatory, that’s not on Adam, it’s on the college.