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 get you probably don't care at all about people who interact with your community but letting bots run free is something I really dislike. I suspect the majority of users feel the same.
Just takes one disgruntled person who is unhappy with you to flood your server without any captcha or other measures taken to prevent it. Might be still under the radar to a degree as of right now but that will not always be the case.
The only way to get rid of the bots is for moderators to pay attention.
That's like saying "My corporation doesn't need anti-virus! we have smart users!"
Defense in depth is the only philosophy that makes sense in this case imo.