At this point, i would recommend :
1. Disable/remove signature for everyone
2. More strict/difficult CAPTCHA
3. Requiring CAPTCHA when post
Maybe new forum will solve all problem we have
Just a few words about captcha. Have you ever seen an entire Chinese (or another Asian, African whatever; it`s just for example) village solving captchas for bots? I have 1. Disable/remove signature for everyone
2. More strict/difficult CAPTCHA
3. Requiring CAPTCHA when post
Maybe new forum will solve all problem we have
$1 for 500 or smth it was. There are still services that provide such help. So I don`t think, this will completely solve the case. But indeed it can make a life more difficult for spammers. And for regular users as well 