This isn't going to open the flood gates of harassment. You can still block accounts from your DMs and mute accounts more generally. Genuine assholes can easily roll new accounts or incite a mob of their own followers, just as they've always done. What this really does is make it harder for petty people to get the last word, and ironically this also includes Elon who's notoriously thin skinned.

If Twitter were to be the digital manifestation of a town square this would arguably bring it one step closer. Public spaces can be cruel and inhospitable places, they were never meant to be your personal safe space.