" Some platforms might have a no nudity policy, some have a zero trolling rule. Others call fair game to all of the above. "
If this all came with a duty of interoperability, I would be fine with that. But walled gardens that do their utmost to make leaving them really unpleasant and possibly expensive to the users ... that sounds a lot like coercion. And European law usually recognizes that individuals coerced, even softly, by large businesses, need protection.
That’s a separate problem though and should be handled like so. Dictating in law what content independent platforms can and cannot disallow doesn’t solve the walled garden problem. It just places greater challenges on new entrants / would-be competitors while still allowing walled gardens to exist. Plus you also then lose the diversity of TOS that might attract new users to new platforms. It’s a lose/lose outcome that doesn’t even attempt to solve the problem you’re identifying.
If this all came with a duty of interoperability, I would be fine with that. But walled gardens that do their utmost to make leaving them really unpleasant and possibly expensive to the users ... that sounds a lot like coercion. And European law usually recognizes that individuals coerced, even softly, by large businesses, need protection.