In an effort to prevent my readers/commenters from experiencing blinding eyestrain, I tried eliminating the Word Verification. That yielded me lots and lots of really stupid spam. So I tried the option of only "registered users," whatever that may be. That produced complaints from commenters who were rejected from commenting. Another option is users with Google accounts, which is what I think is behind the whole thing -- Google wants everyone to have a Google account and supposedly then everyone could comment without word verification. Which would take us back to the dratted spammers.
I'm back to a setting that Anyone can comment, but must use Word Verification. I wish it weren't so.