@BeggarsBeleifWe have one, but it's invisible to most of you because the newest version of reCaptcha doesn't even show itself unless it has a reason to. This is a legit farm with people actually completing Captchas in some cases it would seem. Not normal for us - we get spam all the time, but not on this level because it gets caught by Cloudflare or reCaptcha before it can get very far.
Have some alternative solutions in the works to slow them down for the future like capping the number of PMs that you can send in the first 7 days of your registration (for example).
Hmm, so they have nothing in common? That makes it quite hard to destinguish them from genuine users. If you were to introduce a policy similar to that of Reddit where you cannot post/send messages until you acccount is of a certain age (24hrs).