Hello RougeCat,
Yes, it gets a little tiresome to remove the spammers accounts, so to help I could give you moderation rights so you could help deleting and/or analyzing for counterspamming.
Just tell me if you like to help.
Sorry for the delay, but as you know my connection is weekends-only. I would be able to check it only from Friday to Sunday, so my moderation would be almost unnoticed. I doubt I can be of help that way. I mostly wanted to get advising/ideas to prevent it.
Captchas often work for bots, and many of those looked like an automatic answer based on the thread content. How about adding a "captcha" before making a new posting? I've seen cases of SPAM flooding attacks in other forums that forced the admin to lock all new postings for several days until they cleared it all, because they kept bot-posting and the site was flooded in literally a few minutes. And the problem has been increasing, I fear this forum had to do the same.