I'd rather leave the definition of obscenity to the courts than to a private company.
If a company wants to editorialize their content and provide moderation when they deem fit then they specifically should lose their protections under section 230.
That is completely the opposite of how section 230 works, and section 230 is the entire reason websites like Hacker News are allowed to exist. Your argument has now gotten even worse, not better!
If a company loses Section 230 protections, the safest move is to disable user content completely. No comments anywhere. The next-safest move is to be extremely heavy-handed editorially, since any comment left alone could be the basis for a company-ending lawsuit. Whatever views you believe are being censored now, I guarantee you they would be actually censored completely without Section 230.
Read Section 230[0]. It's the foundation of the modern internet and says almost exactly the opposite of what you're suggesting. Read 230(c)(2)(A) twice.
If a company wants to editorialize their content and provide moderation when they deem fit then they specifically should lose their protections under section 230.