Current US law is extremely clear about the third-party liability that various internet companies have due to user speech. It's limited by Section 230 to knowingly infringing copyright and conduct by the platform that rises to the level of criminal activity (of particular importance is distribution of child pornography). If someone defames you on Twitter or uses it to send you death threats, you cannot successfully sue Twitter, their hosting provider, or their ISP.
The only thing Section 230 has to say about filtering is that you aren't allowed to sue websites over their moderation decisions. The protection of liability for third-party speech is in no way dependent on whether or not the platform does filtering.
The only thing Section 230 has to say about filtering is that you aren't allowed to sue websites over their moderation decisions. The protection of liability for third-party speech is in no way dependent on whether or not the platform does filtering.