I'm now on my regular browser to type this - it was impossible to visit here anonymously.
It can be done, but solving the captchas takes about 5 minutes to register, and another 5 minutes to login. After that you'll most likely have to pay an evil fee before your account can post anything.
But, once you're through, you can get a
Captcha bypass code, and from this moment you can login without captcha on Tor.
There is a lot of discussion in the TOR community that captcha is puposely blocking sites that come from TOR IPs.
I've had that problem many times too. But I can imagine many Tor users are actually up to no good. I have no idea if Tor is often used by bots though.