Okay so this isn't exactly a comment box tutorial BUT this is where I made mine from. The best part about this form is it has PHP included in it. This makes a huge difference to those who use neocities because neocities doesn't support PHP. So, I found this useful and will leave it here ^_^
• also I use the free version, all you have to do is sign up & make an account to make your own form
• you have the choice of moderating the comments or can allow anyone to post
• you can also allow people to post images or not