>>For all the idealistic calls for free speech, I've heard almost no one forward an actual model for free speech that could be applied twitter or some other site.

Twitter acts as a public square, so people should be free to express themselves in any way they want, up to the limits of the law. We want Free Speech in places that act as public squares for the same reason we want the government to respect free speech: it is the only way to ensure critically important contrarian voices are not stifled.

Blocking/filtering algorithms should be open source, with every user free to implement any one that they want for their own feed.