I was trying to understand fluctuations in my S3 cost over time the last few days, where they were mysterious decreases and increases.
I had an idea 
and took a look at the Staff Actions logs in the Discourse admin interface, where I could show the change site settings actions and easily find every time I changed the backup frequencies and retention, which were correlated at and explained the cost variations of my S3 bucket.
I also discovered months ago that Discourse also keeps logs of all the changes regarding themes and components (change theme action), including CSS and HTML, which saved me one time by recovering some CSS code I thought was lost.
These logs are an incredible and powerful tool. 