The reCAPTCHA function requires that humans read distorted words in order to prove that they are real. It’s an industry-accepted method to make sure that comments aren’t flooded by spambots. This has now been implemented on Joe Kitty Threads for making comments and registering as a new user. Once you’ve registered as a user, you won’t have to do the reCAPTCHA to submit comments any more.
In addition to being a security measure and convenience increaser, the reCAPTCHA business uses our human eyes to confirm interpretations of smeared words so that old texts can be digitized, leading to more books available in digital format for all to read.