I'm not doubting you but the only time I can recall ever seeing CAPTCHAs in these forums, or on the Trainz Portal, was in the early days when they were first introduced - I put that down to "fine tuning" issues.
If you are a registered user and are seeing them then put in a HelpDesk request.
Hi AJG747 and Matruck
I have made some adjustments to your account's permissions to make sure that they are configured correctly, if you do still see the 'captcha' appear then please reply to this ticket and we'll look further into it.