If you confirm your email address you will not see a CAPTCHA again.
We're using reCAPTCHA which is accessible in its new incarnation as a simple checkbox, according to
http://simplyaccessible.com/article/googles-no-captcha/
If for any reason you can't use it, you can contact a site admin - email me at alex@textadventures.co.uk and ask me to mark your account email address as confirmed.