Even though I have an account and I am already logged in, I cannot post at SciFi.SE.
Stack Exchange has this annoying CAPTCHA. If I submit a wrong answer to the CAPTCHA, I get: "Oops! Those aren't the correct words", and if I submit a correct one, I get: "An error occurred submitting the CAPTCHA". The result is that I cannot post anything.
Besides, I have an old account with plenty enough reputation across the Stack Exchange network: I would have thought that the software would have known by now that this is not a spammer-operated account! Why is the CAPTCHA so intrusive on normal users?