All good alternatives will have rule, thus moderation.

Where does the line between "free speech" and moderation exists?

The problem is access to platforms. We haven't found a good way to do this. People should be free to opt in or out of the content they want. What offends one will not offend another. For example a thread on hunting will offend some who love the animals they hunt. There is no universal right or wrong there. On should have access to an online community the other should have the ability to disagree or avoid that community. The problem is when an organisation like Twitter picks a side that free speech becomes an issue. Only because of the monopolistic nature of the platform. But that's what makes the platform good, everyone is there.

When free speech on the internet is discussed, it is within the context of freedom from excessive moderation on a platform. To call a Fediverse a "platform" doesn't seem quite analogous, these communities are more like their own platforms that are far more intensely moderated than even Twitter or Reddit.

Free speech advocates who aren't convinced by the "just go to another platform" argument in a discussion about Reddit or Twitter censorship likely won't think the argument is worth accepting simply by redefining what a platform is.

And what stops a network of lemmy instances from being that more intensely moderated Reddit alternatives? That's my point: just because other reddit alternatives have branded themselves as "free speech" doesn't mean all of them have to. And federated platforms might make that easier than one-offs.