I have a little bit of code similar to yours for comments, I just wrote some glue to require Google or Facebook authentication through AWS Cognito to make comments. Some people will hate that, but it worked.

The admin interface could be something that runs local though, would save the time in terms of adding authentication.

I've already had to edit the JSON file on S3 to remove/edit a couple of comments. That was pretty easy to do from the command-line, but I think most people will want a web interface.