I forget to mention there should be another domain (preferable .onion), but normally user only can see login page with input field signed message/PGP signature/certificate and register page which force copper membership.
To prevent spam, there should reCAPTCHA, but configured to allow JS-disabled browser to solve it.
Adding new subdomain will redirect you on main doamin. Once you click loging page than same thing will happen. But I think for reCAPTCHA problem could solve by CAPTCHA.
For Example
9+2=? If use this kind of CAPTCHA I think Tor browser will not face problem.
AFAIK, smart bots can solve
9+2=?. This is the reason big websites are increasingly placing trust on Google's Re-CAPTCHA. Unfortunately, Google's Re-CAPTCHA does not provide
word challenge anymore. All are just images and they dont get solved even if you are correctly pointing them. The reason behind this is Google's machine learning AI is far from perfect as of yet. They assume,
good IP will always correctly solve the captcha. But, they dont. Hence, the irritating problem we face with Tor.