The subprogram CAPTCHA has several defects. Here is a recent thread on the subject.
Can We Get Rid Of The CAPTCHA?There must be something better than CAPTCHA. I tend to generate long post and sometimes they take 30 minutes to create. I submit the post and take a break. Then I come back and there is CAPTHA. Not only that but it has timed out, so now I am into the phase of looking at low resolution photographs to see if I can detect a bridge or crosswalk or bicyclist. Then it seems like the link was posted, but it wasn't. And not only that but my thread was lost. So I have to reenter it from scratch. It almost makes one want to scream!! ! ! ! ! ! !
So when you submit a long complex thread make sure before you submit it that you save it as a scratch file. This is so you can recover it if CAPTCHA bombs. Otherwise you have to enter it all from scratch.