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.
Mine got blown up a day or two ago before I had enabled Captch. About 100 accounts were created before I started getting rate-limited (or similar) by Google.
Better admin tools are definitely needed to handle the scale. We need a pane of glass to see signups and other user details. Hopefully it’s in the works.