@Big Sister, If you're referring to this message:
"Your post has been changed because invalid HTML was found in the message body. The invalid HTML has been removed. Please review the message and submit the message when you are satisfied."
It simply means the post was checked for code that might be problematic. When you see it, just go ahead and click/tap "POST" and you'll see that your reply will be posted with no problem.
Few things reveal your intellect and your generosity of spirit—the parallel powers of your heart and mind—better than how you give feedback.~Maria Popova