That means all the the CP, hate speech — and in this case, piracy — that are posted on Reddit are Reddit’s responsibility.

Of course not, from reddit's ToS: "By submitting Your Content to the Services, you represent and warrant that you have all rights, power, and authority necessary to grant the rights to Your Content contained within these Terms. Because you alone are responsible for Your Content, you may expose yourself to liability if you post or share Content without all necessary rights.

You retain any ownership rights you have in Your Content, but you grant Reddit the following license to use that Content:

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