Twitter was never a healthy "public square" for most of us. Let's not rewrite history while eulogizing the hellsite.
Twitter was a frightening battleground where we managed barely to claw out an uneasy existence amidst the worst violent neo-Nazi extremists who constantly published our home addresses, threatened our kids' lives, and sent hordes of racist trolls into our mentions.
The same principles that allowed us to survive uneasily on Twitter will be required here in the #fediverse. Community defense, thoughtful pressure on moderation policies, and eternal vigilance.
There are no safe spaces but those we make safe through constant effort. We keep us safe.