Please. Captcha by default. Email domain filters. Auto-block federation from servers that don't respect. By default. Urgent.
And yes, to refute some comments, this publication is being upvoted by bots. A single computer was needed, not "thousands of dollars" spent.
I feel like the email analogy sort of breaks down. Email is point to point, not a forum. If there's a Lemmy instance community that acts like the equivalent of the_Donald subreddit and they go around harassing other communities I'd want to defed from that server. I don't want to try to block them one by one.
The benefit (and potential downside) of Lemmy is that there could be several networks of communities. There doesn't have to be a single Lemmy community, but there could many, all with different goals and guidelines. That definitely has pros and cons, but I come down on the opinion that it's overall a good thing.