First, I checked on my blog (http://deborah-teachingonline.blogspot.com) to see if comments worked there. I found that comments weren't working on my blog, much to my surprise. Perhaps it was easier in earlier versions of Blogger (or maybe I just got too clever in the settings for my own good).
I then went to Blogger, logged in, and clicked on Settings for my blog. One of the tabs is Comments, so I clicked on it. There I found many choices, any number of which could have been causing the problem. It was set to Show comments, so that wasn't the problem (but it would have been, if it was set to Hide comments).
I looked at Who can comment? and changed it to Anyone, rather than Members with Google accounts. I saved the changes, then closed and opened my blog again. No good; I had something else wrong.
I looked at Comment form placement and noticed that if you choose Embedded below post, as I had it, meant that Post Pages needed to be enabled. Since I didn't remember if that was the case or not, I just clicked on Pop-up window and saved the changes.
That seemed to do the trick.
I did one more thing: I added my email address in the Comment Notification Email box so that I would get an email when someone commented. I saved the changes again.
I did one more thing: I added my email address in the Comment Notification Email box so that I would get an email when someone commented. I saved the changes again.
Making changes one by one takes more time, but it's the only way to know what really solves a problem.
Someone also asked about adding images. That's actually easier. You can add images to a post by clicking on the image icon (the one that looks like a little picture) when you are writing a post. I've added a picture of my granddaughter looking happy - the way I felt when I figured out how to make the comments work.
Always an adventure!