A few years back, most bloggers have to deal with unwanted spam comments, especially if they had not enabled comments moderation. Because of such widespread spam comments, most bloggers enabled captcha (word verification) for comments in which case commentators would first have to complete the word like the one you see in the screen shot below:
If you allow comments for your posts and moderate your comments, I would highly recommend you do not enable captcha (word verification) for the following reasons:
Ever since all blogging platforms including Blogger add the "nofollow" attribute to hyperlinks in comments, the incentive for spammers to post spam comments have been greatly reduced and I have found that spam comments have reduced to almost zero.
Having to complete word verification is a great inconvenience, especially for the visually impaired who have to click on the universal handicap icon in order for the alphabets in the captcha to be read out in audio form. I have tested clicking on that icon and the resulting machine voice is practically indecipherable. I have captured it on a video. Play the video below and see if you can make out what the voice is trying to say:
In my opinion, captcha is a torture. Why subject your readers to torture when the original reasons for enabling captcha, spam comments, is no longer a problem.
Update: Looks like a few bloggers have a different experience from mine in that they get lots of spam comments. I will like to hear about your experience. Please leave a comment.