Movable Type comment error: “Text entered was wrong. Try again”

After I added some new commenting features to this blog, this error started to appear when comments were submitted:


Comment Submission Error
Your comment submission failed for the following reasons:
Text entered was wrong. Try again."



This was because the Comment, Captcha, Registration and Spam settings were in conflict with each other. I fixed it by using the settings shown below. Try turning off Captcha, make sure you have upgraded to Movable Type 4.37 or later. Then adjust settings as shown below.

You may have to temporarily turn off all commenting, and save, then turn it on again after adjusting settings to get it to work.

Many thanks to Mihai Bocsaru for the solution.