A website that contains both first party and third party content has section 230 protection on the third party content, but none on the first party content. There is no legal basis for the idea of "publisher" as different from "platform". If a website makes a modification to a specific piece of content, they may lose section 230 protections over that particular piece of content, but they retain it on all other 3rd party content.
The FCC cannot change the requirements to gain "platform protection" because there are none, because section 230 applies to content (like a tweet), not entities (like "Twitter").