It's quite an interesting question. There are lots of privately owned 'public' spaces in meatspace, and the function of a space (a place where people get togeth

It's quite an interesting question. There are lots of privately owned 'public' spaces in meatspace, and the function of a space (a place where people get together in public) and its ownership (municipal, commons, private) don't always overlap. Which doesn't necessarily mean that Twitter should be treated as a town square, because it's clearly something different to that. Similar sorts of concerns about the centrality of private spaces to public use led to PruneYard Shopping Center v. Robins, a California case allowing political activity at shopping centres against the wishes of the operator. That case hasn't been widely followed in other states and countries, though, probably for good reasons.