"Codifying a distinction between platform and publisher would require a place like HN to consider either shutting"
This is just false.
'Codifying' distinctions between various services would give places like HN even more clear protections by defining the terms in which they operate.
230 is a recipe for disaster, it's completely the opposite of Net Neutrality and is creating a cold war for information control.
It gives cover for Verizon, Amazon etc. to do whatever they like whenever they like.
'Codifying' the status of the various systems would mean ensuring those in the 'Verizon' category could not filter for anything other than QoS, clarifying terms for those like Amazon, and even distinguishing between different kinds of platforms like Facebook/Twitter an HN.
If the tables were turned on the types of information banned by Amazon, there would be outrage. I can only imagine if Bezos were 'an old Trump buddy' fudding with various customers here and there, what the loudest voices would be saying.
There's nothing arbitrary about these various forms of content and information distribution platforms, it wouldn't be that hard at all to clear things up and ensure fair access.
Combined with a 'User Bill of Rights' (aka right to delete accounts, full transparency on data usage etc.) it would be tremendous progress.