A BSD forum I enjoy is almost spam-free. I mention this one because; in variety of users, attractiveness to spammers, and available time of the moderators and admins; it's the closest comparison to here I know of. These limitations are placed on new users:
* Unable to post links.
* Unable to post any images.
* Unable to use signatures.
* Unable to edit posts.
* No access to some features like social groups, albums, PM, email users, etc.
After 5 days or five posts the restrictions go away. A couple of our spammers have shown a lot of patience and a willingness to do work by hand, so more checking than five days/posts might be necessary here. Some details on
daemonforums' policy are
here.
Please don't contact that poster with forum-related questions, he's since retired after long service. A post to the proper forum would almost definitely get help in this regard from his successors or so. If an admin here would like, I'd do the initial legwork to put you in touch if you prefer.
I don't like the idea of more hassles for new users; new-user-friendliness is one of the things VL forums are rightly known for. But it seems necessary and worth the trade-off, if it's explained when signing up. Not long since I was a new user at daemonforums and had to post a URL to make my meaning clear. No problem -- just posted in in plain text and was easily understood. It's just not spammer-friendly, which is the idea.
I've seen a simpler, lower-bandwidth "captcha" than Captcha. Don't know how it's done, but I can find out if an admin requests.