We're looking into it. Can you tell me if it is happening today? We use SSO so it sounds like you saw captcha before you got into the forum which would suggest you saw captcha on our "support" login. Can you capture screenshots of your browser including the URL of the page that presents the captcha and email it to email@example.com. We do have "captcha" enabled on the forum when a user makes a large amount of comments on the forum in a 24 hour period to prevent spam however it is unlikely that most users would make enough comments in a day to reach this threshold. That captcha will only appear when the threshold has been met before posting a comment or post. You certainly haven't made enough comments to reach that threshold.
Support Forums Manager