If your definition of free speech requires that a platform have no rules whatsoever, then there has never been a free speech platform anywhere on the internet, because such a platform would have to accept illegal content and spam, and could never moderate anything.
But that's not my point, 4chan has clear rules that are not about illegal content: https://4chan.org/rules. There are moderators/janitors enforcing thoses rules and a report system. The first rule is:
"1. You will not upload, post, discuss, request, or link to anything that violates local or United States law."
But that's only the first rule. There are 17 global rules, and each board has a few.
Exactly. My point with Poole is that he started a platform that was much more accepting than competitor sites. Eventually he wasn't happy with how it turned out and walked away from it. Easy enough to do when it's a small operation. But with a larger operation like Twitter staff are invested enough that they won't just say "fuck it". So you see stronger TOSes build up over time.
4chan has never been about free speech, it had rules since the beginning which are constantly enforced.