At bare minimum, if you are by default serving users anything other than a chronological feed of posts from accounts they have chosen to follow, you are not a platform. You are a publisher and subject to all the same rights and responsibilities thereof
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"Here is content from users you don't follow presented to you in the order that we want you to see it. But we're not a publisher. We're just a widdle platform. You can't hold us accountable"
It’s not much unlike a bookstore putting a book in a prominent position, but not being the author of the book.
The book placement doesn’t diminish their liability protection from the contents.