Hello Mike & thanks for this plugin! Been using it for years w/o issue, along with your contact form.
Been getting reports from readers over the passed couple of months that they can't comment as they are being flagged as spam after they enter the captcha & submit. The sites' author also experienced the same when testing, then later that day, I tried commenting from the same ip & did so w/o issue.
The only plugins that I've added that are somewhat new are the Social Sharing Toolkit & Print Friendly, & they were added months before we heard any complaints. It's difficult to test for a plugin conflict as the problem seems intermittent & I would need to rely on readers as well.
Unfortunately, I needed to disable the plugin. I am hoping that you'll be able to remedy whatever it is that is causing the problem. Let me know if there is anything that I can do. Thanks so much & happy New Year!