I found this explanation over at 'Lets Get Sketchy' http://www.letsgetsketchy.blogspot.com.au
Go into your “design” tab
Click the “settings” tab
Then click the “comments” tab
Scroll down to “show word verification for comments” and click NO
Then save settings.
I think mine is turned off but you could let me know if it's still there by leaving a comment on this post.
Thank you for reading and I hope this helps as you may not even know if yours is turned on.