Not sure if my comments are welcome, but I am sure someone will have no problem telling me so if not.
My comments (based on significant experience at the unholy shit I know you’re going through)…
The registration page is wide open to abuse. Its a spammer’s dream. I don’t know what script the site runs on (haven’t even looked) but whatever it is, there is either a dead easy way, or slightly trickier way, to install a captcha (or TWO!). That will turn away 80-90% of spam programs, and reduce your workload that amount too.
Don’t want to teach any egg-sucking, but in case it is not already know (90% sure it is) - when you ban someone, their IP needs to be added to a permanent ban list. The best way to do this is to ban them at server level so they can’t even ever VIEW any SL pages, let alone try signing up.
Revenue could be very easily made out of backlinks on the site. The reason it gets hammered so hard is because the value of a backlink from any page on SL (especially the older threads) is huge. In backlink sales an old site with AUTHORITY is like gold dust these days. Most people know they own a seriously authoritative site and so they leverage that fully. Because SL is more of a community and not run by mercenary mofos (I suspect at least!) it’s great, but it also means the commercial value of the site MAY have been overlooked. If so, get marketing some text backlinks on the site, that will generate plenty of revenue to pay people to deal with spam and moderation etc, and plenty left over I am sure! (and that job shouldn’t be 10-20% of what it is if a few hardened anti-spam techniques are employed/installed.
Finally, if I were running this site myself (I have run a similarly large forum single-handed and went through all this shit myself for years), I would require on the Registration page that people send an email of no less than say 50 or maybe 100 words explaining why they want to join. I know that sounds silly, but seriously, it WILL NOT put off ANYONE who will be a genuine contributor to SL. On the other hand, for people joining to ask, learn, get into shaping etc, they will have plenty to say to fill a 50 word text box! Those emails would go to a specific email inbox (i.e. registration-request@sl.com) where someone would just check them each day, and no reading needed, at a very quick skim/glance it will be blatantly obvious who the spammers are and who the genuine applicants are. If in doubt, I would delete every time. If its a real person with good intentions, they will try again. If its not, they won’t.
Please note, I am fairly sure there will be people among you (the mods etc) who may know every bit of what I just said, so don’t take offence, these are just a few suggestions which I hope may help. If not, i just wasted a few minutes typing and that’s fine by me, especially if it might help keep Viagra vendors off SL! I will shut up now, and wish you luck with it.
Edit/Add - Re: the IP Ban List - I actually went further and assessed the applications, 90% of the spam was coming from Russia and China. Since my site didn’t offer anything to Russians or Chinese people, I banned the COUNTRIES completely, so ANY IP address in either country just got a “Page Not Found” whenever they tried to access my forum in any way. That REALLY helped. Not sure if it’s practical for SL, but I mention it just in case.
Good luck