One time recently when I got the Human Verification screen, I clicked the "I'm A Human" button, then lost track of what I was doing and clicked it again. I think this ended up asking me for verification again, even though it had already received verification and performed the action I'd been requesting. I honestly forget exactly what happened after the second click, but it didn't make sense and seems like a usability problem to me.
Every time since then, I've managed to not click the button again, but if you watch closely, you'll see that the captcha image disappears, and this causes the button to jump upward in the page, almost like it was a new page load and something more needs to be done.
Can the page be rewritten to just sit still until the action is complete and the page is redirected? Why snap the captcha out at all? Or, can the "I'm A Human" button please NOT jump around, or can it become disabled, or something else so I don't have to have the "whoops, don't click on that" hitch every time?
You may see that usually, the "I'm A Human" button flashes by too fast to click on. Just consider that sometimes it is possible, since internet requests can vary in time a lot, depending on many factors.
Okay, so far, I've not been able to duplicate the second click (it goes too fast for me). Maybe it happened one time when the network response was a little slower (thus being the trigger for prompting me to click on it in the first place). In any case, I think it's still an issue, and wish that page elements wouldn't jump around unexpectedly--a usability no-no, for sure.