@macmanx Hi James, I tried your suggestion and turned off all the browser extensions and add-ons but there was still the same problem. However when I tried to make a comment via my phone using Safari that seemed to work so perhaps it is an issue with using Firefox itself. Let me know what you think.
Hi @macmanx,
It works when the Jetpack comments are disabled. I also tested it with someone else putting in a comment but who was not logged in and that seemed to work as well. But the problem happens when I try to post and am logged in to my WordPress account.
@luckynasan Hi Luckyna, I upgraded the Yoast plugin and the Story validates now. Thanks for your help.