Can a platform curate the content on its site to the point where it is legally considered a publisher and loses protection under section 230?
Curating the content, as in displaying it in a certain form or deleting it, is not what differentiates publishers and platforms.
Two things can make a platform a publisher:
- Editing content in certain ways convey a message.
- Adding to content in a way that conveys a message.
Courts have held that Section 230 prevents you from being held liable even if you exercise the usual prerogative of publishers to edit the material you publish. You may also delete entire posts. However, you may still be held responsible for information you provide in commentary or through editing. For example, if you edit the statement, "Fred is not a criminal" to remove the word "not," a court might find that you have sufficiently contributed to the content to take it as your own. Likewise, if you link to an article, but provide a defamatory comment with the link, you may not qualify for the immunity. https://www.eff.org/issues/bloggers/legal/liability/230
If you edit content in a way that makes it defamatory or add defamatory language or content the platform can be liable as a publisher.
I saw that you asked for specific cases in comments, so here is a list.