I just turned mine off, I actually never realized mine was on or how to turn it off. I finally figured it out just now! So you're welcome.
I know it's a pain to leave a comment when you have to type another word in, I have to admit that it has even caused me to not leave comments on other's pages. So I imagine it has caused people to not leave comments here.
Now it's gone, so comment away!!
If you need to know how to do it:
1. Go to Settings on your Dashboard
2. Then click comments on the top.
3. Scroll down to Word Verification and click NO.