The Twitter-like platform Gab has been forced offline, as their payment providers, hosting provider and domain provider all told them their business was no longer welcome. The platform is home to people with extremist views claiming their freedom of speech is under threat. At issue is of course where that speech becomes calling for violence, such as by the Gab-user who horribly murdered 11 people last weekend in Pittsburgh driven by anti-semitic hate.

Will we see an uptick in the use of federated sites such as Mastodon when platforms like Gab that are much more public disappear?

This I think isn’t about extremists being ‘driven underground’ but denying calls for violence, such as happened on Gab, a place in public discourse. An uptick in the use of federated sites would be a good development, as federation allows for much smaller groups to get together around something, whatever it is. In reverse that means no-one else needs to be confronted with it either if they don’t want to. Within the federation of Mastodon sites, I regularly come across instances listing other instances they do not connect to, and for which reasons. It puts the power of supporting welcomed behaviour and pushing back on unwelcome behaviour in the hands of more people, meaning every person running a Mastodon instance (and you can have your own instance), than just Twitter or Facebook management.

example of an instance denying another to be federated with it

That sort of moderation can still be hard, even if the moderator to member ratio is already much better than on the main platforms. But that just points the way to the long tail of much smaller instances, more individual ones even. It means it becomes easier for individuals and small groups to shun small cells, echo-chambers and rage bubbles, and not accidentally ending up in them or being forcefully drawn into them while you were having other conversations, like what can happen on Twitter. See my earlier posting on the disintegration of discourse. You then can do what networks do well: route around the stuff you perceive as damage or non-functional. It creates a stronger power symmetry and communication symmetry. It also denies extremists a wider platform. Yes they can still call for violence, which remains just as despicable. Yes, they can still blame Others for anything and be hateful of them. But they will be doing it in their back yard (or Mastodon instance), not in the park where you like to go walk your dog or do your morning run (or Twitter). They will not have a podium bigger than warranted, they will not have visibility beyond their own in-crowd. And will have to deal with more pushback and reality whenever they step outside such a bubble, without the pleasant illusion ‘everyone on twitter agrees with me’.